ElectroDB

ElectroDB is a dynamodb library to ease the use of having multiple entities and complex hierarchical relationships in a single dynamodb table.

This library is a work in progress, please submit issues/feedback or reach out on twitter @tinkertamper.

Features

• Attribute Schema Enforcement - Define a schema for your entities with enforced attribute validation, defaults, types, aliases, and more.
• Easily Compose Hierarchical Access Patterns - Plan and design hierarchical keys for your indexes to multiply your possible access patterns.
• Single Table Entity Segregation - Entities created with ElectroDB will not conflict with other entities when using a single table.
• Simplified Sort Key Condition Querying - Write efficient sort key queries by easily building compose keys.
• Simplified Filter Composition - Easily create complex readable filters for Dynamo queries without worrying about the implementation of ExpressionAttributeNames, ExpressionAttributeValues.
• Easily Query Across Entities - Define "collections" to create powerful/peformant queries that return multiple entities in a single request.
• Automatic Index Selection - Use .find() method to dynamically and effeciently query based on defined sort key structures.
• Simplified Pagination API - Use .page() to easily iterate through multiquery result sets.
• Use With Your Existing Solution - If you are already using DynamoDB, and want to use ElectroDB, use custom Facet Templates to leverage your existing key structures.
• Generate Type Defintions - Coming Soon: The ability to generate TypeScript .d.ts based on your model.

Turn this:

Employees.query
	.coworkers({ office: "Scranton Branch", team: "marketing" })
	.where(({ salary, title }, { between, contains }) => `
		${ between(salary, "120000", "140000") } AND ${ contains(title, "junior") }
	`)
	.params();

Into This:

{
  KeyConditionExpression: '#pk = :pk and begins_with(#sk1, :sk1)',
  TableName: 'staff',
  ExpressionAttributeNames: {
    '#office': 'office',
    '#team': 'team',
    '#salary': 'salary',
    '#title': 'title',
    '#pk': 'gsi1pk',
    '#sk1': 'gsi1sk'
  },
  ExpressionAttributeValues: {
    ':office1': 'Scranton Branch',
    ':team1': 'marketing',
    ':salary_w1': '120000',
    ':salary_w2': '140000',
    ':title_w1': 'junior',
    ':pk': '$taskapp#office_scranton branch',
    ':sk1': '$workplaces#employees_1#team_marketing#title_'
  },
  IndexName: 'gsi1pk-gsi1sk-index',
  FilterExpression: '(#office = :office1 AND#team = :team1) AND (#salary between :salary_w1 and :salary_w2) AND contains(#title, :title_w1)'
}

Try out the above example for yourself! https://runkit.com/tywalch/creating-and-querying-an-electrodb-service

Table of Contents

• ElectroDB
  • Features
  • Table of Contents
• Installation
• Usage
• Entities and Services
• Entities
• Services
  • Join
  • Model
    • Model Properties
    • Service Properties
    • Model/Service Options
  • Attributes
    • Simple Syntax
    • Expanded Syntax
    • Attribute Validation
  • Indexes
    • Indexes Without Sort Keys
    • Indexes With Sort Keys
  • Facets
    • Facet Arrays
    • Facet Templates
  • Collections
  • Filters
    • Defined on the model
    • Defined via Filter method after query operators
    • Multiple Filters
  • Where
    • FilterExpressions
    • ConditionExpressions
    • Attributes and Operations
    • Multiple Where Clauses
• Building Queries
  • Sort Key Operations
  • Using facets to make hierarchical keys
    • Shopping Mall Stores
  • Query Chains
    • Get Record
    • Delete Record
    • Batch Write - Delete Records
    • Put Record
    • Batch Write - Put Records
    • Update Record
    • Scan Records
    • Patch Records
    • Create Records
    • Find Records
    • Query Records
      • Partition Key Facets
  • Collection Chains
  • Execute Queries
    • Params
    • Go
    • Page
  • Query Examples
  • Query Options
• Examples
  • Employee App
    • Employee App Requirements
    • Entities
    • Query Records
      • All tasks and employee information for a given employee
      • Find all employees and office details for a given office
      • Tasks for a given employee
      • Tasks for a given project
      • Find office locations
      • Find employee salaries and titles
      • Find employee birthdays or anniversaries
      • Find direct reports
  • Shopping Mall Property Management App
    • Shopping Mall Requirements
    • Access Patterns are accessible on the StoreLocation
    • PUT Record
      • Add a new Store to the Mall
    • UPDATE Record
      • Change the Store's Lease Date
    • GET Record
      • Retrieve a specific Store in a Mall
    • DELETE Record
      • Remove a Store location from the Mall
    • Query Records
      • All Stores in a particular mall
      • All Stores in a particular mall building
      • Find the store located in unit B47
      • Stores by Category at Mall
      • Stores by upcoming lease
      • Stores will renewals for Q4
      • Spite-stores with release renewals this year
      • All Latte Larrys in a particular mall building
• Version 1.0 Migration
• Coming Soon

Installation

Install from NPM

npm install electrodb --save

Usage

Require Entity and/or Service from electrodb:

const {Entity, Service} = require("electrodb");

Entities and Services

To see full examples of ElectroDB in action, go to the Examples section.

Entity allows you to create separate and individual business objects in a DynamoDB table. When queried, your results will not include other Entities that also exist the same table. This allows you to easily achieve single table design as recommended by AWS. For more detail, read Entities.

Service allows you to build a relationships across Entities. A service imports Entity Models, builds individual Entities, and creates Collections to allow cross Entity querying. For more detail, read Services.

You can use Entities independent of Services, you do not need to import models into a Service to use them individually. However, If you intend to make queries that join or span multiple Entities you will need to use a Service.

Entities

In ElectroDB an Entity is represents a single business object. For example, in a simple task tracking application, one Entity could represent an Employee and or a Task that the employee is assigned to.

Require or import Entity from electrodb:

const {Entity} = require("electrodb");

Services

In ElectroDB a Service represents a collection of Entities and also allows you to build queries span across Entities. Similar to Entities, Services can coexist on a single table without collision. You can use Entities independent of Services, you do not need to import models into a Service to use them individually. However, you do you need to use a Service if you intend make queries that join multiple Entities.

Require electrodb:

const {Service} = require("electrodb");

Join

Create individual (Entities)[#entities] with the (Models)[#models] or join them via a Service.

// Independent Models
let table = "my_table_name";
let employees = new Entity(EmployeesModel, { client, table });
let tasks = new Entity(TasksModel, { client, table });

// Joining Entity instances to a Service
let TaskApp = new Service("TaskApp", { client, table });
TaskApp
	.join(employees) // available at TaskApp.entities.employees
	.join(tasks);    // available at TaskApp.entities.tasks

// Joining models to a Service
let TaskApp = new Service("TaskApp", { client, table });
TaskApp
	.join(EmployeesModel) // available at TaskApp.entities.employees
	.join(TasksModel);    // available at TaskApp.entities.tasks

When joining a Model/Entity to a Service a number of validations are done to ensure that Entity conforms to expectations collectively established by all joined Entities.

• Entity names must be unique across a Service.
• Collection names must be unique accross a Service.
• The name of the Service in the Model must match the Name defined on the Service instance.
• Joined instances must be type Model or Entity.
• If the attributes of an Entity have overlapping names with other attributes in that service, they must all have compatible or matching attribute options.
• All primary and global secondary indexes must have the same name field names and be written to assume SortKeys exist/don't exist in the same manor. See Indexes.
• All models conform to the same model format. If your model was made pre-electrodb version 0.9.19 see section Version 1 Migration.

Model

Create an Entity's schema. In the below example.

const DynamoDB = require("aws-sdk/clients/dynamodb");
const {Entity, Service} = require("electrodb");
const client = new DynamoDB.DocumentClient();
const EmployeesModel = {
	model: {
		entity: "employees",
		version: "1",
		service: "taskapp",
	},
	attributes: {
		employee: {
			type: "string",
			default: () => uuidv4(),
		},
		firstName: {
			type: "string",
			required: true,
		},
		lastName: {
			type: "string",
			required: true,
		},
		office: {
			type: "string",
			required: true,
		},
		title: {
			type: "string",
			required: true,
		},
		team: {
			type: ["development", "marketing", "finance", "product", "cool cats and kittens"],
			required: true,
		},
		salary: {
			type: "string",
			required: true,
		},
		manager: {
			type: "string",
		},
		dateHired: {
			type: "string",
			validate: /^\d{4}-\d{2}-\d{2}$/gi
		},
		birthday: {
			type: "string",
			validate: /^\d{4}-\d{2}-\d{2}$/gi
		},
	},
	indexes: {
		employee: {
			pk: {
				field: "pk",
				facets: ["employee"],
			},
			sk: {
				field: "sk",
				facets: [],
			},
		},
		coworkers: {
			index: "gsi1pk-gsi1sk-index",
			collection: "workplaces",
			pk: {
				field: "gsi1pk",
				facets: ["office"],
			},
			sk: {
				field: "gsi1sk",
				facets: ["team", "title", "employee"],
			},
		},
		teams: {
			index: "gsi2pk-gsi2sk-index",
			pk: {
				field: "gsi2pk",
				facets: ["team"],
			},
			sk: {
				field: "gsi2sk",
				facets: ["title", "salary", "employee"],
			},
		},
		employeeLookup: {
			collection: "assignments",
			index: "gsi3pk-gsi3sk-index",
			pk: {
				field: "gsi3pk",
				facets: ["employee"],
			},
			sk: {
				field: "gsi3sk",
				facets: [],
			},
		},
		roles: {
			index: "gsi4pk-gsi4sk-index",
			pk: {
				field: "gsi4pk",
				facets: ["title"],
			},
			sk: {
				field: "gsi4sk",
				facets: ["salary", "employee"],
			},
		},
		directReports: {
			index: "gsi5pk-gsi5sk-index",
			pk: {
				field: "gsi5pk",
				facets: ["manager"],
			},
			sk: {
				field: "gsi5sk",
				facets: ["team", "office", "employee"],
			},
		},
	},
	filters: {
		upcomingCelebrations: (attributes, startDate, endDate) => {
			let { dateHired, birthday } = attributes;
			return `${dateHired.between(startDate, endDate)} OR ${birthday.between(
				startDate,
				endDate,
			)}`;
		},
	},
};

const TasksModel = {
	model: {
		entity: "tasks",
		version: "1",
		service: "taskapp",
	},
	attributes: {
		task: {
			type: "string",
			default: () => uuidv4(),
		},
		project: {
			type: "string",
		},
		employee: {
			type: "string",
		},
		description: {
			type: "string",
		},
	},
	indexes: {
		task: {
			pk: {
				field: "pk",
				facets: ["task"],
			},
			sk: {
				field: "sk",
				facets: ["project", "employee"],
			},
		},
		project: {
			index: "gsi1pk-gsi1sk-index",
			pk: {
				field: "gsi1pk",
				facets: ["project"],
			},
			sk: {
				field: "gsi1sk",
				facets: ["employee", "task"],
			},
		},
		assigned: {
			collection: "assignments",
			index: "gsi3pk-gsi3sk-index",
			pk: {
				field: "gsi3pk",
				facets: ["employee"],
			},
			sk: {
				field: "gsi3sk",
				facets: ["project", "task"],
			},
		},
	},
};

Model Properties

Property	Description
model.service	Name of the application using the entity, used to namespace all entities
model.entity	Name of the entity that the schema represents
model.version	(optional) The version number of the schema, used to namespace keys
attributes	An object containing each attribute that makes up the schema
indexes	An object containing table indexes, including the values for the table's default Partition Key and Sort Key
filters	An object containing user defined filter template functions

Model Service Options

Optional second parameter

Property	Description
table	Name of the dynamodb table in aws
client	(optional) An instance of the docClient from the aws-sdk for use when querying a DynamoDB table. This is optional if you wish to only use the params functionality, but required if you actually need to query against a database.

Attributes

Attributes define an Entity record. The AttributeName represents the value your code will use to represent an attribute.

Pro-Tip: Using the field property, you can map an AttributeName to a different field name in your table. This can be useful to utilize existing tables, existing models, or even to reduce record sizes via shorter field names. For example, you may refer to an attribute as organization but want to save the attribute with a field name of org in DynamoDB.

Simple Syntax

Assign just the type of the attribute directly to the attribute name. Currently supported options are "string", "number", "boolean", an array of strings representing a fixed set of possible values, or "any" which disables value type checking on that attribute.

attributes: {
	<AttributeName>: "string"|"number"|"boolean"|"any"|string[]
}

Expanded Syntax

Use the expanded syntax build out more robust attribute options.

attributes: {
	<AttributeName>: {
		"type": string|string[],
		"required"?: boolean,
		"default"?: value|() => value
		"validate"?: RegExp|(value: any) => void|string
		"field"?: string
		"readOnly"?: boolean
		"label"?: string
		"cast"?: "number"|"string"|"boolean",
		"get"?: (attribute, schema) => value,
		"set"?: (attribute, schema) => value 
	}
}

Property	Type	Required	Description
type	string, string[]	yes	Accepts the values: "string", "number" "boolean", an array of strings representing a finite list of acceptable values: ["option1", "option2", "option3"], or "any"which disables value type checking on that attribute.
required	boolean	no	Whether or not the value is required when creating a new record.
default	value, () => value	no	Either the default value itself or a synchronous function that returns the desired value.
validate	RegExp, (value: any) => void, (value: any) => string	no	Either regex or a synchronous callback to return an error string (will result in exception using the string as the error's message), or thrown exception in the event of an error.
field	string	no	The name of the attribute as it exists dynamo, if named differently in the schema attributes. Defaults to the AttributeName as defined in the schema.
readOnly	boolean	no	Prevents update of the property after the record has been created. Attributes used in the composition of the table's primary Partition Key and Sort Key are by read-only by default.
label	string	no	Used in index composition to prefix key facets. By default, the AttributeName is used as the label.
cast	"number", "string", "boolean"	no	Optionally cast attribute values when interacting with DynamoDB. Current options include: "number", "string", and "boolean".
set	(attribute, schema) => value	no	A synchronous callback allowing you apply changes to a value before it is set in params or applied to the database. First value represents the value passed to ElectroDB, second value are the attributes passed on that update/put
get	(attribute, schema) => value	no	A synchronous callback allowing you apply changes to a value after it is retrieved from the database. First value represents the value passed to ElectroDB, second value are the attributes retrieved from the database.

Attribute Validation

The validation property allows for many different function/type signatures. Here the different combinations ElectroDB supports:

signature	behavior
Regexp	ElectroDB will call .test(val) on the provided regex with the value passed to this attribute
(value: T) => string	If a string with length is returned from validate it will be considered the reason an the value is invalid. It will generate an error message with this reason.
(value: T) => boolean	If a boolean is returned, true or truthy values will signify than a value is invalid while false or falsey will be considered valid
(value: T) => void	A void/undefined return will be treated as successful, in this scenario you can throw an Error yourself to interrupt the query

Indexes

The indexes object requires at least the definition of the table's natural Partition Key and (if applicable) Sort Key.

Indexes are defined, and later referenced by their AccessPatternName. These defined via a facets array that is made up of attributes names as listed the model.

indexes: {
	<AccessPatternName>: {
		"pk": {
			"field": <string>
			"facets": <AttributeName[]>
		},
		"sk"?: {
			"field": <string>
			"facets": <AttributesName[]>
		},
		"index"?: string
		"collection"?: string
	}
}

Property	Type	Required	Description
pk	object	yes	Configuration for the pk of that index or table
pk.facets	boolean	no	An array that represents the order in which attributes are concatenated to facets the key (see Facets below for more on this functionality).
pk.field	string	yes	The name of the attribute as it exists dynamo, if named differently in the schema attributes.
sk	object	no	Configuration for the sk of that index or table
sk.facets	`array	string`	no
sk.field	string	yes	The name of the attribute as it exists dynamo, if named differently in the schema attributes.
index	string	no	Required when the Index defined is a Secondary Index; but is left blank for the table's primary index.
collection	string	no	Used when models are joined to a Service. When two entities share a collection on the same index, they can be queried with one request to DynamoDB. The name of the collection should represent what the query would return as a pseudo Entity. (see Collections below for more on this functionality).

Indexes Without Sort Keys

When using indexes without Sort Keys, that should be expressed as an index without an sk property at all. Indexes without an sk cannot have a collection, see (Collections)[[#collections] for more detail.

Note: It is generally recommended to have Sort Keys when using ElectroDB as they allow for more advanced query opportunities. Even if your model doesnt need an additional property to define a unique record, having an sk with no facets still opens the door to many more query opportunities like (collections)[#collections].

// ElectroDB interprets as index *not having* an SK.
{
  indexes: {
    myIndex: {
      pk: {
        field: "pk",
        facets: ["id"]
      }
    }
  }
}

Indexes With Sort Keys

When using indexes with Sort Keys, that should be expressed as an index with an sk property. If you don't wish to use the sk in your model, but it does exist on the table, simply use an empty for the facets property. This is still useful as it opens the door to many more query opportunities like (collections)[#collections].

// ElectroDB interprets as index *having* SK, but this model doesnt attach any facets to it.
{
  indexes: {
    myIndex: {
      pk: {
        field: "pk",
        facets: ["id"]
      },
      sk: {
        field: "sk",
        facets: []
      }
    }
  }
}

Facets

A Facet is a segment of a key based on one of the attributes. Facets are concatenated together from either a Partition Key or an Sort Key key, which define an index.

Note: Only attributes with a type of "string", "number", or "boolean" can be used as a facet

There are two ways to provide facets:

1. As a Facet Array
2. As a Facet Template

For example, in the following Access Pattern, "locations" is made up of the facets storeId, mallId, buildingId and unitId which map to defined attributes in the schema:

// Input
{
    storeId: "STOREVALUE",
    mallId: "MALLVALUE",
    buildingId: "BUILDINGVALUE",
    unitId: "UNITVALUE"
};

// Output:
{
	pk: '$mallstoredirectory_1#storeId_storevalue',
	sk: '$mallstores#mallid_mallvalue#buildingid_buildingvalue#unitid_unitvalue'
}

For PK values, the service and version values from the model are prefixed onto the key.

For SK values, the entity value from the model is prefixed onto the key.

Facet Arrays

In a Facet Array, each element is the name of the corresponding Attribute defined in the Model. If the Attribute has a label property, that will be used to prefix the facets, otherwise the full Attribute name will be used.

attributes: {
	storeId: {
		type: "string",
		label: "sid",
	},
	mallId: {
		type: "string",
		label: "mid",
	},
	buildingId: {
		type: "string",
		label: "bid",
	},
	unitId: {
		type: "string",
		label: "uid",
	}
},
indexes: {
	locations: {
		pk: {
			field: "pk",
			facets: ["storeId"]
		},
		sk: {
			field: "sk",
			facets: ["mallId", "buildingId", "unitId"]
		}
	}
}
    
// Input
{
    storeId: "STOREVALUE",
    mallId: "MALLVALUE",
    buildingId: "BUILDINGVALUE",
    unitId: "UNITVALUE"
};

// Output:
{
	pk: '$mallstoredirectory_1#sid_storevalue',
	sk: '$mallstores#mid_mallvalue#bid_buildingvalue#uid_unitvalue'
}

Facet Templates

In a Facet Template, you provide a formatted template for ElectroDB to use when making keys. Facet Templates allow for potential ElectroDB adoption on already established tables and records.

Attributes are identified by a prefixed colon and the attributes name. For example, the syntax :storeId will matches storeId attribute in the model.

Convention for a composing a key use the # symbol to separate attributes, and for labels to attach with underscore. For example, when composing both the mallId and buildingId would be expressed as mid_:mallId#bid_:buildingId.

ElectroDB will not prefix templated keys with the Entity, Project, Version, or Collection. This will give you greater control of your keys but will limit ElectroDB's ability to prevent leaking entities with some queries.

Facet Templates have some "gotchas" to consider: 1. Keys only allow for one instance of an attribute, the template :prop1#:prop1 will be interpreted the same as :prop1#. 2. ElectoDB will continue to always add a trailing delimiter to facets with keys are partially supplied. (More documentation coming on this soon)

attributes: {
	storeId: {
		type: "string"
	},
	mallId: {
		type: "string"
	},
	buildingId: {
		type: "string"
	},
	unitId: {
		type: "string"
	}
},
indexes: {
	locations: {
		pk: {
			field: "pk",
			facets: "sid_:storeId"
		},
		sk: {
			field: "sk",
			facets: "mid_:mallId#bid_:buildingId#uid_:unitId"
		}
	}
}


// Input
{
    storeId: "STOREVALUE",
    mallId: "MALLVALUE",
    buildingId: "BUILDINGVALUE",
    unitId: "UNITVALUE"
};

// Output:
{
	pk: 'sid_storevalue',
	sk: 'mid_mallvalue#bid_buildingvalue#uid_unitvalue'
}

Collections

A Collection is a grouping of Entities with the same Partition Key and allows you to make efficient query across multiple entities. If you background is SQL, imagine Partition Keys as Foreign Keys, a Collection represents a View with multiple joined Entities.

Collections are defined on an Index, and the name of the collection should represent what the query would return as a pseudo Entity. Additionally Collection names must be unique across a Service.

Note: collection should be unique to a single common index across entities.

Using the TaskApp Models defined in Models, these models share a collection called assignments on the index gsi3pk-gsi3sk-index

let TaskApp =  new  Service("projectmanagement", { client, table: "projectmanagement" }); 
TaskApp
	.join(EmployeesModel) // TaskApp.entities.employees
	.join(TasksModel);    // TaskApp.entities.tasks

TaskApp.collections.assignments({employee: "JExotic"}).params();

// Results
{
  TableName: 'projectmanagement',
  ExpressionAttributeNames: { '#pk': 'gsi3pk', '#sk1': 'gsi3sk' },
  ExpressionAttributeValues: { ':pk': '$taskapp_1#employee_joeexotic', ':sk1': '$assignments' },
  KeyConditionExpression: '#pk = :pk and begins_with(#sk1, :sk1)',
  IndexName: 'gsi3pk-gsi3sk-index'
}

Filters

Filters are no longer the preferred way to add FilterExpressions. Checkout the Where section to find out about how to apply FilterExpressions and ConditionExpressions

Building thoughtful indexes can make queries simple and performant. Sometimes you need to filter results down further. By adding Filters to your model, you can extend your queries with custom filters. Below is the traditional way you would add a filter to Dynamo's DocumentClient directly along side how you would accomplish the same using a Filter function.

{
  IndexName: 'idx2',
  TableName: 'StoreDirectory',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Defined on the model

Filters can defined on the model and used in your query chain.

/**
	* Filter by low rent a specific mall or a leaseEnd withing a specific range  
	* @param {Object} attributes - All attributes from the model with methods for each filter operation  
	* @param {...*} values - Values passed when calling the filter in a query chain.
**/
filters: {
	rentPromotions: function(attributes, minRent, maxRent, promotion)  {
		let {rent, discount} = attributes;
		return `
			${rent.between(minRent, maxRent)} AND ${discount.lte(promotion)}
		`
	}
}


let StoreLocations  =  new Entity(model, {table: "StoreDirectory"});
let maxRent = "5000.00";
let minRent = "2000.00";
let promotion = "1000.00";
let stores  =  MallStores.query
	.stores({ mallId: "EastPointe" })
	.between({ leaseEndDate:  "2020-04-01" }, { leaseEndDate:  "2020-07-01" })
	.rentPromotions(minRent, maxRent, promotion)
	.params();

// Results
{
  IndexName: 'idx2',
  TableName: 'StoreDirectory',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Defined via Filter method after query operators

The easiest way to use filters is to use them inline in your query chain.

let StoreLocations  =  new Entity(model, {table: "StoreDirectory"});
let maxRent = "5000.00";
let minRent = "2000.00";
let promotion = "1000.00";
let stores  =  StoreLocations.query
	.leases({ mallId: "EastPointe" })
	.between({ leaseEndDate:  "2020-04-01" }, { leaseEndDate:  "2020-07-01" })
	.filter(({rent, discount}) => `
		${rent.between(minRent, maxRent)} AND ${discount.lte(promotion)}
	`)
	.params();

// Results
{
  IndexName: 'idx2',
  TableName: 'StoreDirectory',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND #discount <= :discount1'
}

Filter functions allow you to write a FilterExpression without having to worry about the complexities of expression attributes. To accomplish this, ElectroDB injects an object attributes as the first parameter to all Filter Functions. This object contains every Attribute defined in the Entity's Model with the following operators as methods:

operator	example	result
gte	rent.gte(maxRent)	#rent >= :rent1
gt	rent.gt(maxRent)	#rent > :rent1
lte	rent.lte(maxRent)	#rent <= :rent1
lt	rent.lt(maxRent)	#rent < :rent1
eq	rent.eq(maxRent)	#rent = :rent1
begins	rent.begins(maxRent)	begins_with(#rent, :rent1)
exists	rent.exists()	attribute_exists(#rent)
notExists	rent.notExists()	attribute_not_exists(#rent)
contains	rent.contains(maxRent)	contains(#rent = :rent1)
notContains	rent.notContains(maxRent)	not contains(#rent = :rent1)
between	rent.between(minRent, maxRent)	(#rent between :rent1 and :rent2)
name	rent.name()	#rent
value	rent.value(maxRent)	:rent1

This functionality allows you to write the remaining logic of your FilterExpression with ease. Add complex nested and/or conditions or other FilterExpression logic while ElectroDB handles the ExpressionAttributeNames and ExpressionAttributeValues.

Multiple Filters

It is possible to include chain multiple filters. The resulting FilterExpressions are concatinated with an implicit AND operator.

let MallStores = new Entity(model, {table: "StoreDirectory"});
let stores = MallStores.query
	.leases({ mallId: "EastPointe" })
	.between({ leaseEndDate: "2020-04-01" }, { leaseEndDate: "2020-07-01" })
	.filter(({ rent, discount }) => `
		${rent.between("2000.00", "5000.00")} AND ${discount.eq("1000.00")}
	`)
	.filter(({ category }) => `
		${category.eq("food/coffee")}
	`)
	.params();

// Results
{
  TableName: 'StoreDirectory',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#category': 'category',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':category1': 'food/coffee',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#storeid_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#storeid_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  IndexName: 'idx2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND (#discount = :discount1 AND #category = :category1)'
}

Where

The where() method is an improvement on the filter() method. Unlike filter, where will be compatible with upcoming features related to complex types.

Building thoughtful indexes can make queries simple and performant. Sometimes you need to filter results down further or add conditions to an update/patch/put/create/delete action.

FilterExpressions

Below is the traditional way you would add a FilterExpression to Dynamo's DocumentClient directly along side how you would accomplish the same using the where method.

{
  KeyConditionExpression: '#pk = :pk and begins_with(#sk1, :sk1)',
  TableName: 'zoodirectory',
  ExpressionAttributeNames: {
    '#animal': 'animal',
    '#lastFed': 'lastFed',
    '#pk': 'pk',
    '#sk1': 'sk'
  },
  ExpressionAttributeValues: {
    ':animal_w1': 'Warthog',
    ':lastFed_w1': '2020-09-25',
    ':lastFed_w2': '2020-09-28',
    ':pk': '$zoodirectory_1#habitat_africa',
    ':sk1': '$exibits#enclosure_'
  },
  FilterExpression: '#animal = :animal_w1 AND (#lastFed between :lastFed_w1 and :lastFed_w2)'
}

animals.query
		.farm({habitat: "Africa"})
		.where(({animal, dangerous}, {value, name, between}) => `
			${name(animal)} = ${value(animal, "Warthog")} AND ${between(dangerous, "2020-09-25", "2020-09-28")}
		`)
		.params()

ConditionExpressions

Below is the traditional way you would add a ConditionExpression to Dynamo's DocumentClient directly along side how you would accomplish the same using the where method.

{
  UpdateExpression: 'SET #dangerous = :dangerous',
  ExpressionAttributeNames: { '#animal': 'animal', '#dangerous': 'dangerous' },
  ExpressionAttributeValues: {
    ':animal_w1': 'Zebra',
    ':dangerous_w1': false,
    ':dangerous': true
  },
  TableName: 'zoodirectory',
  Key: {
    pk: '$zoodirectory_1#habitat_africa',
    sk: '$exibits#enclosure_5b'
  },
  ConditionExpression: '#animal = :animal_w1 AND #dangerous = :dangerous_w1'
}

animals.update({habitat: "Africa", enclosure: "5b"})
	.set({dangerous: true})
	.where(({animal, dangerous}, {value, name, eq}) => `
		${name(animal)} = ${value(animal, "Zebra")} AND ${eq(dangerous)}
	`)
	.params())

Attributes and Operations

Where functions allow you to write a FilterExpression or ConditionExpression without having to worry about the complexities of expression attributes. To accomplish this, ElectroDB injects an object attributes as the first parameter to all Filter Functions, and an object operations, as the second parameter. Pass the properties from the attributesobject to the methods found on theoperations` object, along with inline values to set filters and conditions:

// A single filter operation
animals.update({habitat: "Africa", enclosure: "5b"})
	.set({keeper: "Joe Exotic"})
	.where((attr, op) => op.eq(attr.dangerous, true))
	.params());

// Multiple conditions
animals.update({habitat: "Africa", enclosure: "5b"})
	.set({keeper: "Joe Exotic"})
	.where((attr, op) => `
		${op.eq(attr.dangerous, true)} AND ${op.contains(attr.diet, "meat")}
	`)
	.params());

The attributes object contains every Attribute defined in the Entity's Model. The operations object contains the following methods:

operator	example	result
gte	gte(rent, value)	#rent >= :rent1
gt	gt(rent, maxRent)	#rent > :rent1
lte	lte(rent, maxRent)	#rent <= :rent1
lt	lt(rent, maxRent)	#rent < :rent1
eq	eq(rent, maxRent)	#rent = :rent1
begins	begins(rent, maxRent)	begins_with(#rent, :rent1)
exists	exists(rent)	attribute_exists(#rent)
notExists	notExists(rent)	attribute_not_exists(#rent)
contains	contains(rent, maxRent)	contains(#rent = :rent1)
notContains	notContains(rent, maxRent)	not contains(#rent = :rent1)
between	between(rent, minRent, maxRent)	(#rent between :rent1 and :rent2)
name	name(rent)	#rent
value	value(rent, maxRent)	:rent1

Multiple Where Clauses

It is possible to include chain multiple where clauses. The resulting FilterExpressions (or ConditionExpressions) are concatinated with an implicit AND operator.

let MallStores = new Entity(model, {table: "StoreDirectory"});
let stores = MallStores.query
	.leases({ mallId: "EastPointe" })
	.between({ leaseEndDate: "2020-04-01" }, { leaseEndDate: "2020-07-01" })
	.where(({ rent, discount }, {between, eq}) => `
		${between(rent, "2000.00", "5000.00")} AND ${eq(discount, "1000.00")}
	`)
	.where(({ category }, {eq}) => `
		${eq(category, "food/coffee")}
	`)
	.params();

// Results
{
  TableName: 'StoreDirectory',
  ExpressionAttributeNames: {
    '#rent': 'rent',
    '#discount': 'discount',
    '#category': 'category',
    '#pk': 'idx2pk',
    '#sk1': 'idx2sk'
  },
  ExpressionAttributeValues: {
    ':rent1': '2000.00',
    ':rent2': '5000.00',
    ':discount1': '1000.00',
    ':category1': 'food/coffee',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-04-01#storeid_',
    ':sk2': '$mallstore#leaseenddate_2020-07-01#storeid_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  IndexName: 'idx2',
  FilterExpression: '(#rent between :rent1 and :rent2) AND (#discount = :discount1 AND #category = :category1)'
}

Building Queries

Forming a composite Partition Key and Sort Key is a critical step in planning Access Patterns in DynamoDB. When planning composite keys, it is crucial to consider the order in which they are composed. As of the time of writing this documentation, DynamoDB has the following constraints that should be taken into account when planning your Access Patterns:

1. You must always supply the Partition Key in full for all queries to DynamoDB.
2. You currently only have the following operators available on a Sort Key: begins_with, between, >, >=, <, <=, and Equals.
3. To act on single record, you will need to know the full Partition Key and Sort Key for that record.

Sort Key Operations

operator	use case
begins_with	Keys starting with a particular set of characters.
between	Keys between a specified range.
eq	Keys equal to some value
gt	Keys less than some value
gte	Keys less than or equal to some value
lt	Keys greater than some value
lte	Keys greater than or equal to some value

Using facets to make hierarchical keys

Carefully considering your Facet order will allow *ElectroDB to express hierarchical relationships and unlock more available Access Patterns for your application.

For example, let's say you have a StoreLocations Entity that represents Store Locations inside Malls:

Shopping Mall Stores

let schema = {  
    model: {
      service: "MallStoreDirectory",  
      entity: "MallStore",
      version: "1",    
    },  
	attributes: {  
		mallId: {  
			type: "string",  
			required: true,  
		},  
		storeId: {  
			type: "string",  
			required: true,  
		},  
		buildingId: {  
			type: "string",  
			required: true,  
		},  
		unitId: {  
			type: "string",  
			required: true,
		},  
		category: {  
			type: [
				"spite store",
				"food/coffee", 
				"food/meal", 
				"clothing", 
				"electronics", 
				"department", 
				"misc"
			],  
			required: true  
		},  
		leaseEndDate: {  
			type: "string",  
			required: true  
		},
		rent: {
			type: "string",
			required: true,
			validate: /^(\d+\.\d{2})$/
		},
		discount: {
			type: "string",
			required: false,
			default: "0.00",
			validate: /^(\d+\.\d{2})$/
		}  
	},  
	indexes: {  
	    stores: {  
			pk: {
				field: "pk",
				facets: ["storeId"]
			}, 
			sk: {
				field: "sk",
				facets: ["mallId", "buildingId", "unitId"]
			}  
		},  
		malls: {  
			index: "idx1",  
			pk: {
				field: "idx1pk",
				facets: ["mallId"]
			},  
			sk: {
				field: "idx1sk",
				facets: ["buildingId", "unitId", "storeId"]
			}  
		},
		leases: {
			index: "idx2",
			pk: {
				field: "idx2pk",
				facets: ["mallId"]
			},  
			sk: {
				field: "idx2pk",
				facets: ["leaseEndDate", "storeId", "buildingId", "unitId"]
			}  
		}
	},
	filters: {
		byCategory: ({category}, name) => category.eq(name),
		rentDiscount: (attributes, discount, max, min) => {
			return `${attributes.discount.lte(discount)} AND ${attributes.rent.between(max, min)}`
		}
	}  
};
const StoreLocations = new Entity(schema, {table: "StoreDirectory"});

Each record represents one Store location. All Stores are located in Malls we manage.

To satisfy requirements for searching based on location, you could use the following keys: Each StoreLocations record would have a Partition Key with the store's storeId. This key alone is not enough to identify a particular store. To solve this, compose a Sort Key for the store's location attribute ordered hierarchically (mall/building/unit): ["mallId", "buildingId", "unitId"].

The StoreLocations entity above, using just the stores Index alone enables four Access Patterns:

1. All LatteLarrys locations in all Malls
2. All LatteLarrys locations in one Mall
3. All LatteLarrys locations inside a specific Mall
4. A specific LatteLarrys inside of a Mall and Building

Query Chains

Queries in ElectroDB are built around the Access Patterns defined in the Schema and are capable of using partial key Facets to create performant lookups. To accomplish this, ElectroDB offers a predictable chainable API.

Examples in this section using the StoreLocations schema defined above.

The methods: Get (get), Create (put), Update (update), and Delete (delete) *require all facets described in the Entities' primary PK and SK.

Get Method

Provide all facets in an object to the get method

await StoreLocations.get({
	storeId: "LatteLarrys", 
	mallId: "EastPointe", 
	buildingId: "BuildingA1", 
	unitId: "B47"
}).go();

// Equivalent Params:
// {
//   Key: {
//     pk: '$mallstoredirectory_1#storeid_lattelarrys',
//     sk: '$mallstore#mallid_eastpointe#buildingid_buildinga1#unitid_b47'
//   },
//   TableName: 'StoreDirectory'
// }

Delete Method

Provide all facets in an object to the delete method to delete a record.

await StoreLocations.delete({
	storeId: "LatteLarrys", 
	mallId: "EastPointe", 
	buildingId: "BuildingA1", 
	unitId: "B47"
}).go();

// Equivalent Params:
// {
//   Key: {
//     pk: '$mallstoredirectory_1#storeid_lattelarrys',
//     sk: '$mallstore#mallid_eastpointe#buildingid_buildinga1#unitid_b47'
//   },
//   TableName: 'StoreDirectory'
// }

Batch Write Delete Records

Provide all facets in an array of objects to the delete method to batch delete records.

Note: Performing a Batch Delete will return an array of "unProcessed" records. An empty array signifies all records were processed. If you want the raw DynamoDB response you can always use the option {raw: true}, more detail found here: Query Options.

await StoreLocations.delete([
  {
    id: "abc",
    sector: "A1",
  }, {
    id: "def",
    sector: "A1",
  }, {
    id: "hij",
    sector: "A1",
  }
]).go();

// Equivalent Params:
// {
// 	"RequestItems":{
// 			"electro":[
// 				{
// 						"DeleteRequest":{
// 							"Key":{
// 									"pk":"$bugbeater#sector_a1",
// 									"sk":"$test_entity_1#id_abc"
// 							}
// 						}
// 				},
// 				{
// 						"DeleteRequest":{
// 							"Key":{
// 									"pk":"$bugbeater#sector_a1",
// 									"sk":"$test_entity_1#id_def"
// 							}
// 						}
// 				},
// 				{
// 						"DeleteRequest":{
// 							"Key":{
// 									"pk":"$bugbeater#sector_a1",
// 									"sk":"$test_entity_1#id_hij"
// 							}
// 						}
// 				}
// 			]
// 	}
// }

Put Record

Provide all required Attributes as defined in the model to create a new record. ElectroDB will enforce any defined validations, defaults, casting, and field aliasing.

let store = {
	storeId: "LatteLarrys",
	mallId: "EastPointe",
	buildingId: "BuildingA1",
	unitId: "B47",
	category: "food/coffee",
	leaseEndDate: "2020-03-22",
	rent: "1500.00"
};

await StoreLocations.put(store).go();

// Equivalent Params:
// {
//   Item: {
//     mallId: 'EastPointe',
//     storeId: 'LatteLarrys',
//     buildingId: 'BuildingA1',
//     unitId: 'B47',
//     category: 'food/coffee',
//     leaseEndDate: '2020-03-22',
//     rent: '1500.00',
//     discount: '0.00',
//     pk: '$mallstoredirectory_1#storeid_lattelarrys',
//     sk: '$mallstore#mallid_eastpointe#buildingid_buildinga1#unitid_b47',
//     idx1pk: '$mallstoredirectory_1#mallid_eastpointe',
//     idx1sk: '$mallstore#buildingid_buildinga1#unitid_b47#storeid_lattelarrys',
//     idx2pk: '$mallstore#leaseenddate_2020-03-22#storeid_lattelarrys#buildingid_buildinga1#unitid_b47',
//     __edb_e__: 'MallStore'
//   },
//   TableName: 'StoreDirectory'
// }

Batch Write Put Records

Provide all required Attributes as defined in the model to create records as an array to .put(). ElectroDB will enforce any defined validations, defaults, casting, and field aliasing.

Note: Performing a Batch Put will return an array of "unProcessed" records. An empty array signifies all records were processed. If you want the raw DynamoDB response you can always use the option {raw: true}, more detail found here: Query Options.

let stores = [
  {
    id: "abc",
    mall: "WashingtonSquare",
    store: "LatteLarrys",
    sector: "A1",
    category: "food/coffee",
    leaseEnd: "2020-01-20",
    rent: "0.00",
    building: "BuildingZ",
    unit: "G1",
  }, {
    id: "def",
    mall: "WashingtonSquare",
    store: "LatteLarrys",
    sector: "A1",
    category: "food/coffee",
    leaseEnd: "2020-01-20",
    rent: "0.00",
    building: "BuildingZ",
    unit: "G1",
  }, {
    id: "hij",
    mall: "WashingtonSquare",
    store: "LatteLarrys",
    sector: "A1",
    category: "food/coffee",
    leaseEnd: "2020-01-20",
    rent: "0.00",
    building: "BuildingZ",
    unit: "G1",
  }
];

await StoreLocations.put(stores).go();

// Equivalent Params:
// {
// 	"RequestItems":{
// 			"electro":[
// 				{
// 						"PutRequest":{
// 							"Item":{
// 									"storeLocationId":"abc",
// 									"sector":"A1",
// 									"mallId":"WashingtonSquare",
// 									"storeId":"LatteLarrys",
// 									"buildingId":"BuildingZ",
// 									"unitId":"G1",
// 									"category":"food/coffee",
// 									"leaseEnd":"2020-01-20",
// 									"rent":"0.00",
// 									"pk":"$bugbeater#sector_a1",
// 									"sk":"$test_entity_1#id_abc",
// 									"gsi1pk":"mall_washingtonsquare",
// 									"gsi1sk":"b_buildingz#u_g1#s_lattelarrys",
// 									"gsi2pk":"m_washingtonsquare",
// 									"gsi2sk":"l_2020-01-20#s_lattelarrys#b_buildingz#u_g1",
// 									"gsi3pk":"$bugbeater#mall_washingtonsquare",
// 									"gsi3sk":"$test_entity_1#category_food/coffee#building_buildingz#unit_g1#store_lattelarrys",
// 									"gsi4pk":"$bugbeater#store_lattelarrys",
// 									"gsi4sk":"$test_entity_1#mall_washingtonsquare#building_buildingz#unit_g1",
// 									"__edb_e__":"TEST_ENTITY",
// 									"__edb_v__":"1"
// 							}
// 						}
// 				},
// 				{
// 						"PutRequest":{
// 							"Item":{
// 									"storeLocationId":"def",
// 									"sector":"A1",
// 									"mallId":"WashingtonSquare",
// 									"storeId":"LatteLarrys",
// 									"buildingId":"BuildingZ",
// 									"unitId":"G1",
// 									"category":"food/coffee",
// 									"leaseEnd":"2020-01-20",
// 									"rent":"0.00",
// 									"pk":"$bugbeater#sector_a1",
// 									"sk":"$test_entity_1#id_def",
// 									"gsi1pk":"mall_washingtonsquare",
// 									"gsi1sk":"b_buildingz#u_g1#s_lattelarrys",
// 									"gsi2pk":"m_washingtonsquare",
// 									"gsi2sk":"l_2020-01-20#s_lattelarrys#b_buildingz#u_g1",
// 									"gsi3pk":"$bugbeater#mall_washingtonsquare",
// 									"gsi3sk":"$test_entity_1#category_food/coffee#building_buildingz#unit_g1#store_lattelarrys",
// 									"gsi4pk":"$bugbeater#store_lattelarrys",
// 									"gsi4sk":"$test_entity_1#mall_washingtonsquare#building_buildingz#unit_g1",
// 									"__edb_e__":"TEST_ENTITY",
// 									"__edb_v__":"1"
// 							}
// 						}
// 				},
// 				{
// 						"PutRequest":{
// 							"Item":{
// 									"storeLocationId":"hij",
// 									"sector":"A1",
// 									"mallId":"WashingtonSquare",
// 									"storeId":"LatteLarrys",
// 									"buildingId":"BuildingZ",
// 									"unitId":"G1",
// 									"category":"food/coffee",
// 									"leaseEnd":"2020-01-20",
// 									"rent":"0.00",
// 									"pk":"$bugbeater#sector_a1",
// 									"sk":"$test_entity_1#id_hij",
// 									"gsi1pk":"mall_washingtonsquare",
// 									"gsi1sk":"b_buildingz#u_g1#s_lattelarrys",
// 									"gsi2pk":"m_washingtonsquare",
// 									"gsi2sk":"l_2020-01-20#s_lattelarrys#b_buildingz#u_g1",
// 									"gsi3pk":"$bugbeater#mall_washingtonsquare",
// 									"gsi3sk":"$test_entity_1#category_food/coffee#building_buildingz#unit_g1#store_lattelarrys",
// 									"gsi4pk":"$bugbeater#store_lattelarrys",
// 									"gsi4sk":"$test_entity_1#mall_washingtonsquare#building_buildingz#unit_g1",
// 									"__edb_e__":"TEST_ENTITY",
// 									"__edb_v__":"1"
// 							}
// 						}
// 				}
// 			]
// 	}
// }

Update Record

To update a record, pass all facets to the update method and then pass set attributes that need to be updated.

Note: If your update includes changes to an attribute that is also a facet for a global secondary index, you must provide all facets for that index.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let category = "food/meal";

await StoreLocations
	.update({storeId, mallId, buildingId, unitId})
	.set({category})
	.go();

// Equivalent Params:
// {
//   UpdateExpression: 'SET #category = :category',
//   ExpressionAttributeNames: { '#category': 'category' },
//   ExpressionAttributeValues: { ':category': 'food/meal' },
//   TableName: 'StoreDirectory',
//   Key: {
//     pk: '$mallstoredirectory_1#storeid_lattelarrys',
//     sk: '$mallstore#mallid_eastpointe#buildingid_buildinga1#unitid_b47'
//   }
// }

Scan Records

When scanning for rows, you can use filters the same as you would any query. For more detial on filters, see the Where section.

Note: Scan functionality will be scoped to your Entity. This means your results will only include records that match the Entity defined in the model.

await StoreLocations.scan
	.filter(({category}) => `
		${category.eq("food/coffee")} OR ${category.eq("spite store")}  
	`)
	.filter(({leaseEndDate}) => `
		${leaseEndDate.between("2020-03", "2020-04")}
	`)
	.go();

// Equivalent Params:
// {
//   TableName: 'StoreDirectory',
//   ExpressionAttributeNames: {
//     '#category': 'category',
//     '#leaseEndDate': 'leaseEndDate',
//     '#pk': 'pk',
//     '#sk': 'sk'
//   },
//   ExpressionAttributeValues: {
//     ':category1': 'food/coffee',
//     ':category2': 'spite store',
//     ':leaseEndDate1': '2020-03',
//     ':leaseEndDate2': '2020-04',
//     ':pk': '$mallstoredirectory_1#storeid_',
//     ':sk': '$mallstore#mallid_'
//   },
//   FilterExpression: '(begins_with(#pk, :pk) AND begins_with(#sk, :sk)) AND (#category = :category1 OR #category = :category2) AND (#leaseEndDate between :leaseEndDate1 and :leaseEndDate2)'
// }

Patch Records

In DynamoDB, update operations by default will insert a record if record being updated does not exist. In ElectroDB, the patch method will utilize the attribute_exists() parameter dynamically to ensure records are only "patched" and not inserted when updating.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let category = "food/meal";

await StoreLocations
	.patch({storeId, mallId, buildingId, unitId})
	.set({category})
  .go()

// Equivalent Params:
// {
//   UpdateExpression: 'SET #category = :category',
//   ExpressionAttributeNames: { '#category': 'category' },
//   ExpressionAttributeValues: { ':category': 'food/meal' },
//   TableName: 'StoreDirectory',
//   Key: {
//     pk: '$mallstoredirectory_1#storeid_lattelarrys',
//     sk: '$mallstore#mallid_eastpointe#buildingid_buildinga1#unitid_b47'
//   },
//   ConditionExpression: 'attribute_exists(pk) AND attribute_exists(sk)'
// }

Create Records

In DynamoDB, put operations by default will overwrite a record if record being updated does not exist. In ElectroDB, the patch method will utilize the attribute_not_exists() parameter dynamically to ensure records are only "created" and not overwriten when inserting new records into the table.

let store = {
	storeId: "LatteLarrys",
	mallId: "EastPointe",
	buildingId: "BuildingA1",
	unitId: "B47",
	category: "food/coffee",
	leaseEndDate: "2020-03-22",
  rent: "1500.00"
};

await StoreLocations.create(store).go();

// Equivalent Params:
// {
//   Item: {
//     mallId: 'EastPointe',
//     storeId: 'LatteLarrys',
//     buildingId: 'BuildingA1',
//     unitId: 'B47',
//     category: 'food/coffee',
//     leaseEndDate: '2020-03-22',
//     rent: '1500.00',
//     discount: '0.00',
//     pk: '$mallstoredirectory_1#storeid_lattelarrys',
//     sk: '$mallstore#mallid_eastpointe#buildingid_buildinga1#unitid_b47',
//     idx1pk: '$mallstoredirectory_1#mallid_eastpointe',
//     idx1sk: '$mallstore#buildingid_buildinga1#unitid_b47#storeid_lattelarrys',
//     idx2pk: '$mallstore#leaseenddate_2020-03-22#storeid_lattelarrys#buildingid_buildinga1#unitid_b47',
//     __edb_e__: 'MallStore'
//   },
//   TableName: 'StoreDirectory',
//   ConditionExpression: 'attribute_not_exists(pk) AND attribute_not_exists(sk)'
// }

Find Records

DynamoDB offers three methods to find records: get, query, and scan. In ElectroDB, there is a fourth type: find. Unlike get and query, the find method does not require you to provide keys, but under the covers it will leverage the attributes provided to find the best index to query on. Provide the find method will all properties known to match a record and ElectroDB will generate the most performant query it can to locate the results. This can be helpful with highly dynamic querying needs. If an index cannot be satisfied with the attributes provided, scan will be used as a last resort.

let match = await StoreLocations.find({
	mallId: "EastPointe",
	buildingId: "BuildingA1",
	leaseEndDate: "2020-03-22",
  rent: "1500.00"
}).go()

// Equivalent Params:
// {
//   KeyConditionExpression: '#pk = :pk and begins_with(#sk1, :sk1)',
//   TableName: 'StoreDirectory',
//   ExpressionAttributeNames: {
//     '#mallId': 'mallId',
//     '#buildingId': 'buildingId',
//     '#leaseEndDate': 'leaseEndDate',
//     '#storeId': 'storeId',
//     '#rent': 'rent',
//     '#pk': 'idx2pk',
//     '#sk1': 'idx2pk'
//   },
//   ExpressionAttributeValues: {
//     ':mallId1': 'EastPointe',
//     ':buildingId1': 'BuildingA1',
//     ':leaseEndDate1': '2020-03-22',
//     ':storeId1': "LatteLarry's",
//     ':rent1': '1500.00',
//     ':pk': '$mallstoredirectory_1#mallid_eastpointe',
//     ':sk1': "$mallstore#leaseenddate_2020-03-22#storeid_lattelarry's#buildingid_buildinga1#unitid_"
//   },
//   IndexName: 'idx2',
//   FilterExpression: '#mallId = :mallId1 AND#buildingId = :buildingId1 AND#leaseEndDate = :leaseEndDate1 AND#storeId = :storeId1 AND#rent = :rent1'
// }

Query Records

Examples in this section using the MallStore schema defined above.

All queries start from the Access Pattern defined in the schema.

const MallStore = new Entity(schema, {table: "StoreDirectory"}); 
// Each Access Pattern is available on the Entity instance
// MallStore.query.stores()
// MallStore.query.malls()

Partition Key Facets

All queries require (at minimum) the Facets included in its defined Partition Key. They can be supplied in the order they are composed or in a single object when invoking the Access Pattern.

const MallStore = new Entity(schema, {table: "StoreDirectory"});
//	stores
//	pk: ["storeId"]
//	sk: ["mallId", "buildingId", "unitId"]

let storeId = "LatteLarrys";
let mallId = "EastPointe";

// Good: As an object
MallStore.query.stores({storeId});

// Bad: Facets missing, will throw
MallStore.query.stores(); // err: Params passed to ENTITY method, must only include storeId

// Bad: Facets not included, will throw
MallStore.query.stores({mallId}); // err: Params passed to ENTITY method, must only include storeId

After invoking the Access Pattern with the required Partition Key Facets, you can now choose what Sort Key Facets are applicable to your query. Examine the table in Sort Key Operations for more information on the available operations on a Sort Key.

Collection Chains

Collections allow you to query across Entities. To use them you need to join your Models onto a Service instance.

Using the TaskApp Models defined in Models, these models share a collection called assignments on the index gsi3pk-gsi3sk-index

const table = "projectmanagement";
const TaskApp = new Service("projectmanagement",  { client, table }); 

TaskApp
	.join(EmployeesModel) // TaskApp.entities.employees
	.join(TasksModel);    // TaskApp.entities.tasks

Available on your Service are two objects: entites and collections. Entities available on entities have the same capabilities as they would if created individually. When a Model added to a Service with join however, its Collections are automatically added and validated with the other Models joined to that Service. These Collections are available on collections.

TaskApp.collections.assignments({employee: "JExotic"}).params();  

// Results
{
  TableName: 'projectmanagement',
  ExpressionAttributeNames: { '#pk': 'gsi3pk', '#sk1': 'gsi3sk' },
  ExpressionAttributeValues: { ':pk': '$taskapp_1#employee_joeexotic', ':sk1': '$assignments' },
  KeyConditionExpression: '#pk = :pk and begins_with(#sk1, :sk1)',
  IndexName: 'gsi3pk-gsi3sk-index'
}

Collections do not have the same query functionality and as an Entity, though it does allow for inline filters like an Entity. The attributes available on the filter object include all attributes across entities.

TaskApp.collections
	.assignments({employee: "CBaskin"})
	.filter((attributes) => `
		${attributes.project.notExists()} OR ${attributes.project.contains("murder")}
	`)

// Results
{
  TableName: 'projectmanagement',
  ExpressionAttributeNames: { '#project': 'project', '#pk': 'gsi3pk', '#sk1': 'gsi3sk' },
  ExpressionAttributeValues: {
    ':project1': 'murder',
    ':pk': '$taskapp_1#employee_carolbaskin',
    ':sk1': '$assignments'
  },
  KeyConditionExpression: '#pk = :pk and begins_with(#sk1, :sk1)',
  IndexName: 'gsi3pk-gsi3sk-index',
  FilterExpression: '\n\t\tattribute_not_exists(#project) OR contains(#project, :project1)\n\t'
}

Execute Queries

Lastly, all query chains end with either a .go() or a .params() method invocation. These will either execute the query to DynamoDB (.go()) or return formatted parameters for use with the DynamoDB docClient (.params()).

Both .params() and .go() take a query configuration object which is detailed more in the section Query Options.

Params

The params method ends a query chain, and synchronously formats your query into an object ready for the DynamoDB docClient.

For more information on the options available in the config object, checkout the section Query Options.

let config = {};
let stores = MallStores.query
    .leases({ mallId })
    .between(
      { leaseEndDate:  "2020-06-01" }, 
      { leaseEndDate:  "2020-07-31" })
    .filter(attr) => attr.rent.lte("5000.00"))
    .params(config);

// Results:
{
  IndexName: 'idx2',
  TableName: 'electro',
  ExpressionAttributeNames: { '#rent': 'rent', '#pk': 'idx2pk', '#sk1': 'idx2sk' },
  ExpressionAttributeValues: {
    ':rent1': '5000.00',
    ':pk': '$mallstoredirectory_1#mallid_eastpointe',
    ':sk1': '$mallstore#leaseenddate_2020-06-01#rent_',
    ':sk2': '$mallstore#leaseenddate_2020-07-31#rent_'
  },
  KeyConditionExpression: '#pk = :pk and #sk1 BETWEEN :sk1 AND :sk2',
  FilterExpression: '#rent <= :rent1'
}

Go

The go method ends a query chain, and asynchronously queries DynamoDB with the client provided in the model.

For more information on the options available in the config object, check out the section Query Options.

let config = {};
let stores = MallStores.query
	.leases({ mallId })
	.between(
		{ leaseEndDate:  "2020-06-01" }, 
		{ leaseEndDate:  "2020-07-31" })
	.filter(({rent}) => rent.lte("5000.00"))
	.go(config);

Page

As of September 29th 2020 the .page() now returns the facets that make up the ExclusiveStartKey instead of the ExclusiveStartKey itself. To get back only the ExclusiveStartKey, add the flag exclusiveStartKeyRaw to your query options. If you treated this value opaquely no changes are needed, or if you used the raw flag.

The page method ends a query chain, and asynchronously queries DynamoDB with the client provided in the model. Unlike the .go(), the .page() method returns a tupple.

The first element for (Entity)[#entity] page query is the "page": an object contains the facets that make up the ExclusiveStartKey that is returned by the DynamoDB client. This is very useful in multi-tenant applications where only some facets are exposed to the client, or there is a need to prevent leaking keys between entities. If there is no ExclusiveStartKey this value will be null. On subsequent calls to .page(), pass the results returned from the previous call to .page() or construct the facets yourself.

The first element for (Collection)[#collections] page query is the ExclusiveStartKey as it was returned by the DynamoDB client.

Note: It is highly recommended to use the lastEvaluatedKeyRaw flag when using .page() in conjunction with scans. This is because when using scan on large tables the docClient may return an ExclusiveStartKey for a record that does not belong to entity making the query (regardless of the filters set). In these cases ElectroDB will return null (to avoid leaking the keys of other entities) when further pagination may be needed to find your records.

The second element is the results of the query, exactly as it would be returned through a query operation.

Note: When calling .page() the first argument is reserved for the "page" returned from a previous query, the second parameter is for Query Options. For more information on the options available in the config object, check out the section Query Options.

let [page, stores] = await MallStores.query
	.leases({ mallId })
	.page();

let [pageTwo, moreStores] = await MallStores.query
	.leases({ mallId })
	.page(page, {});

// page:
// { 
//   storeId: "LatteLarrys", 
//   mallId: "EastPointe", 
//   buildingId: "BuildingA1", 
//   unitId: "B47"
// }

// stores
// [{
//   mall: '3010aa0d-5591-4664-8385-3503ece58b1c',
//   leaseEnd: '2020-01-20',
//   sector: '7d0f5c19-ec1d-4c1e-b613-a4cc07eb4db5',
//   store: 'MNO',
//   unit: 'B5',
//   id: 'e0705325-d735-4fe4-906e-74091a551a04',
//   building: 'BuildingE',
//   category: 'food/coffee',
//   rent: '0.00'
// },
// {
//   mall: '3010aa0d-5591-4664-8385-3503ece58b1c',
//   leaseEnd: '2020-01-20',
//   sector: '7d0f5c19-ec1d-4c1e-b613-a4cc07eb4db5',
//   store: 'ZYX',
//   unit: 'B9',
//   id: 'f201a1d3-2126-46a2-aec9-758ade8ab2ab',
//   building: 'BuildingI',
//   category: 'food/coffee',
//   rent: '0.00'
// }]

Query Examples

Below are all chain possibilities available.

Assume an index named leases defined as:

leases: {
	index: "gsi1pk-gsi1sk-index",
	pk: {
		field: "pk",
		facets: ["mallId"]
	},
	sk: {
		field: "sk",
		facets: ["leaseEndDate", "rent"]
	}
}

And the following model defined filters:

filters: {
	byCategory: ({category}, name) => category.eq(name),
	rentDiscount: (attributes, discount, max, min) => {
		return `${attributes.discount.lte(discount)} AND ${attributes.rent.between(max, min)}`
	}
}  

let mallId = "EastPointe";

// begins_with
MallStore.query.leases({mallId}).go()
MallStore.query.leases({mallId, leaseEndDate: "2020-03"}}).go();
MallStore.query.leases({mallId, leaseEndDate: "2020-03-22", rent: "2000.00"}).go();

// gt, gte, lt, lte
MallStore.query.leases({mallId}).gt({leaseEndDate}).go();
MallStore.query.leases({mallId}).gte({leaseEndDate}).go();
MallStore.query.leases({mallId}).lt({leaseEndDate}).go();
MallStore.query.leases({mallId}).lte({leaseEndDate}).go();

// between
MallStore.query.leases({mallId}).between({leaseEndDate: "2020-03"}, {leaseEndDate: "2020-04"}).go();

// filters -- applied after any of the sort key operators above 
let june = "2020-06";
let july = "2020-07"; 
let discount = "500.00";
let maxRent = "2000.00";
let minRent = "5000.00";

// inline filter
MallStore.query
  .leases({mallId, leaseEndDate: june})
  .filter(attr => attr.storeId.eq("LatteLarrys"))
  .go();

// model defined filters
MallStore.query
  .leases({mallId, leaseEndDate: june})
  .rentDiscount(discount, maxRent, minRent)
  .go();

MallStore.query
  .leases({mallId})
  .between(
    {leaseEndDate: june}, 
    {leaseEndDate: july})
  .byCategory("food/coffee")
  .go();
  

Query Options

By default ElectroDB enables you to work with records as the names and properties defined in the model. Additionally, it removes the need to deal directly with the docClient parameters which can be complex for a team without as much experience with DynamoDB. The Query Options object can be passed to both the .params() and .go() methods when building you query. Below are the options available:

let options = {
	params?: object,
	raw?: boolean,
	includeKeys?: boolean,
	originalErr?: boolean,
	lastEvaluatedKeyRaw?: boolean
};

Option	Description
params	Properties added to this object will be merged onto the params sent to the document client. Any conflicts with ElectroDB will favor the params specified here.
raw	Returns query results as they were returned by the docClient.
includeKeys	By default, ElectroDB does not return partition, sort, or global keys in its response.
originalErr	By default, ElectroDB alters the stacktrace of any exceptions thrown by the DynamoDB client to give better visibility to the developer. Set this value equal to true to turn off this functionality and return the error unchanged.
lastEvaluatedKeyRaw	Used in .pages()calls to override ElectroDBs default behaviour to break apart LastEvaluatedKeys into facets. See more in the (Pages)[#pages] section.

Errors:

Error Code	Description
1000s	Configuration Errors
2000s	Invalid Queries
3000s	User Defined Errors
4000s	DynamoDB Errors
5000s	Unexpected Errors

No Client Defined On Model

Code: 1001

Why this occurred: If a DynamoDB DocClient is not passed to the constructor of an Entity or Service (client), ElectroDB will be unable to query DynamoDB. This error will only appear when a query(using go()) is made because ElectroDB is still useful without a DocClient through the use of it's params() method.

What to do about it: For an Entity be sure to pass the DocClient as the second param to the constructor:

new Entity(schema, {client})

For a Service, the client is passed the same way, as the second param to the constructor:

new Service("", {client});

Invalid Identifier

Code: 1002

Why this occurred: You tried to modify the entity identifier on an Entity.

What to do about it: Make sure the you spelled the identifier correctly or that you actually passed a replacement.

Invalid Key Facet Template

Code: 1003

Why this occurred: You are trying to use the custom Key Facet Template and the format you passed is invalid.

What to do about it: Checkout the section on Facet Templates and verify your template conforms to the rules detailed there.

Duplicate Indexes

Code: 1004

Why this occurred: Your model contains duplicate indexes. This could be because you accidentally included an index twice or even forgot to add an index name on a secondary index, which would be interpreted as "duplicate" to the Table's Primary index.

What to do about it: Double check your indexes as theyre defined on the model for duplicate indexes. The error should specify which index has been duplicated.

{
  indexes: {
    index1: {
      index: "idx1", // <-- duplicate "idx1"
      pk: {},
      sk: {}
    },
    index2: {
      index: "idx1", // <-- duplicate "idx1"
      pk: {},
      sk: {}
    }
  }
}

Collection Without An SK

Code: 1005

Why this occurred: You have added a collection to an index that does not have an SK. Because Collections are used to help query across entities via the Sort Key, not having a Sort Key on an index defeats the purpose of a Collection.

What to do about it: If your index does have an sk but youre unsure of how to inform electro without setting facets to the SK, add the SK object to the index and use an empty array for Facets:

// ElectroDB interprets as index *not having* an SK.
{
  indexes: {
    myIndex: {
      pk: {
        field: "pk",
        facets: ["id"]
      }
    }
  }
}

// ElectroDB interprets as index *having* SK, but this model doesnt attach any facets to it.
{
  indexes: {
    myIndex: {
      pk: {
        field: "pk",
        facets: ["id"]
      },
      sk: {
        field: "sk",
        facets: []
      }
    }
  }
}

Duplicate Collections

Code: 1006

Why this occurred: You have assigned the same collection name to multiple indexes. This is not allowed because collection names must be unique.

What to do about it: Determine a new naming scheme

Missing Primary Index

Code: 1007

Why this occurred: DynamoDB requires the definition of at least one Primary Index on the table. In Electro this is defined as an Index without an index property. Each model needs at least one, and the facets used for this index must ensure each composite represents a unique record.

What to do about it: Identify the index youre using as the Primary Index and ensure it does not have an index property on it's definition.

// ElectroDB interprets as the Primary Index because it lacks an `index` property.
{
  indexes: {
    myIndex: {
      pk: {
        field: "pk",
        facets: ["org"]
      },
      sk: {
        field: "sk",
        facets: ["id"]
      }
    }
  }
}

// ElectroDB interprets as a Global Secondary Index because it has an `index` property.
{
  indexes: {
    myIndex: {
      index: "gsi1"
      pk: {
        field: "gsipk1",
        facets: ["org"]
      },
      sk: {
        field: "gsisk1",
        facets: ["id"]
      }
    }
  }
}

Invalid Attribute Definition

Code: 1008

Why this occurred: Some attribute on your model has an invalid configuration.

What to do about it: Use the error to identify which column needs to examined, double check the properties on that attribute. Checkout the section on (Attributes)[#attributes] for more information on how they are structured.

Invalid Model

Code: 1009

Why this occurred: Some properties on your model are missing or invalid.

What to do about it: Checkout the section on (Models)[#model] to verify your model against what is expected.

Invalid Options

Code: 1010

Why this occurred: Some properties on your options object are missing or invalid.

What to do about it: Checkout the section on (Model/Service Options)[#model-service-options] to verify your model against what is expected.

Duplicate Index Fields

Code: 1014

Why this occurred: An Index in your model references the same field twice across indexes. The field property in the definition of an index is a mapping to the name of the field assigned to the the PK or SK of an index.

What to do about it: This is likely a typo, if not double check the names of the fields you assigned to be the PK and SK of your index, these field names must be unique.

Duplicate Index Facets

Code: 1014

Why this occurred: Within one index you tried to use the same facet in both the PK and SK. A facet may only be used once within an index. With electrodb it is not uncommon to use the same value as both the PK and SK when when a Sort Key exists on a table -- this usually is done because some value is required in that column but for that entity it is not neccessary. If this is your situation remember that ElectroDB does put a value in the SortKey even if does not include a facet, checkout (this seciton)[#collection-without-an-sk] for more information.

What to do about it: Determine how you can change your access pattern to not duplicate the facet. Remember that an empty array for an SK is valid.

Missing Facets

Code: 2002

Why this occurred: The current request is missing some facets to complete the query based on the model definition. Facets are used to create the Partition and Sort keys. In DynamoDB Partition keys cannot be partially included, and Sort Keys can be partially include they must be at least passed in the order they are defined on the model.

What to do about it: The error should describe the missing facets, ensure those facets are included in the query or update the model to reflect the needs of the access pattern.

Invalid Last Evaluated Key

Code: 4002

Why this occurred: Likely you were were calling .page() on a scan. If you werent please make an issue and include as much detail about your query as possible.

What to do about it: It is highly recommended to use the exclusiveStartKeyRaw flag when using .page() in conjunction with scans. This is because when using scan on large tables the docClient may return an ExclusiveStartKey for a record that does not belong to entity making the query (regardless of the filters set). In these cases ElectroDB will return null (to avoid leaking the keys of other entities) when further pagination may be needed to find your records.

// example
model.scan.page({exclusiveStartKeyRaw: true});

aws-error

Code: 4001

Why this occurred: DynamoDB didnt like something about your query.

What to do about it: By default electrodb tries to keep the stack trace close to your code, ideally this can help you identify what might be going on. A tip to help with troubleshooting: use .params() to get insight into how your query is being converted to DocClient params.

Unknown Error

Examples

Employee App

For an example, lets look at the needs of application used to manage Employees. The application Looks at employees, offices, tasks, and projects.

Employee App Requirements

1. As Project Manager I need to find all tasks and details on a specific employee.
2. As a Regional Manager I need to see all details about an office and its employees
3. As an Employee I need to see all my Tasks.
4. As a Product Manager I need to see all the tasks for a project.
5. As a Client I need to find a physical office close to me.
6. As a Hiring manager I need to find employees with comparable salaries.
7. As HR I need to find upcoming employee birthdays/anniversaries
8. As HR I need to find all the employees that report to a specific manager

Entities

const EmployeesModel = {
	model: {
	  entity: "employees",
      version: "1",
      service: "taskapp",  
	},
	attributes: {
		employee: "string",
		firstName: "string",
		lastName: "string",
		office: "string",
		title: "string",
		team: ["development", "marketing", "finance", "product"],
		salary: "string",
		manager: "string",
		dateHired: "string",
		birthday: "string",
	},
	indexes: {
		employee: {
			pk: {
				field: "pk",
				facets: ["employee"],
			},
			sk: {
				field: "sk",
				facets: [],
			},
		},
		coworkers: {
			index: "gsi1pk-gsi1sk-index",
			collection: "workplaces",
			pk: {
				field: "gsi1pk",
				facets: ["office"],
			},
			sk: {
				field: "gsi1sk",
				facets: ["team", "title", "employee"],
			},
		},
		teams: {
			index: "gsi2pk-gsi2sk-index",
			pk: {
				field: "gsi2pk",
				facets: ["team"],
			},
			sk: {
				field: "gsi2sk",
				facets: ["title", "salary", "employee"],
			},
		},
		employeeLookup: {
			collection: "assignements",
			index: "gsi3pk-gsi3sk-index",
			pk: {
				field: "gsi3pk",
				facets: ["employee"],
			},
			sk: {
				field: "gsi3sk",
				facets: [],
			},
		},
		roles: {
			index: "gsi4pk-gsi4sk-index",
			pk: {
				field: "gsi4pk",
				facets: ["title"],
			},
			sk: {
				field: "gsi4sk",
				facets: ["salary", "employee"],
			},
		},
		directReports: {
			index: "gsi5pk-gsi5sk-index",
			pk: {
				field: "gsi5pk",
				facets: ["manager"],
			},
			sk: {
				field: "gsi5sk",
				facets: ["team", "office", "employee"],
			},
		},
	},
	filters: {
		upcomingCelebrations: (attributes, startDate, endDate) => {
			let { dateHired, birthday } = attributes;
			return `${dateHired.between(startDate, endDate)} OR ${birthday.between(
				startDate,
				endDate,
			)}`;
		},
	},
};

const TasksModel = {
	model: {
		entity: "tasks",
    	version: "1",
    	service: "taskapp",  
	}, 
	attributes: {
		task: "string",
		project: "string",
		employee: "string",
		description: "string",
	},
	indexes: {
		task: {
			pk: {
				field: "pk",
				facets: ["task"],
			},
			sk: {
				field: "sk",
				facets: ["project", "employee"],
			},
		},
		project: {
			index: "gsi1pk-gsi1sk-index",
			pk: {
				field: "gsi1pk",
				facets: ["project"],
			},
			sk: {
				field: "gsi1sk",
				facets: ["employee", "task"],
			},
		},
		assigned: {
			collection: "assignements",
			index: "gsi3pk-gsi3sk-index",
			pk: {
				field: "gsi3pk",
				facets: ["employee"],
			},
			sk: {
				field: "gsi3sk",
				facets: ["project", "task"],
			},
		},
	},
};

const OfficesModel = {
	model: {
  		entity: "offices",
      	version: "1",
      	service: "taskapp",  
  	}, 
	attributes: {
		office: "string",
		country: "string",
		state: "string",
		city: "string",
		zip: "string",
		address: "string",
	},
	indexes: {
		locations: {
			pk: {
				field: "pk",
				facets: ["country", "state"],
			},
			sk: {
				field: "sk",
				facets: ["city", "zip", "office"],
			},
		},
		office: {
			index: "gsi1pk-gsi1sk-index",
			collection: "workplaces",
			pk: {
				field: "gsi1pk",
				facets: ["office"],
			},
			sk: {
				field: "gsi1sk",
				facets: [],
			},
		},
	},
};

Join models on a new Service called EmployeeApp

const DynamoDB = require("aws-sdk/clients/dynamodb");
const client = new DynamoDB.DocumentClient({region: "us-east-1"});
const { Service } = require("electrodb");
const table = "projectmanagement";
const EmployeeApp = new Service("EmployeeApp", { client, table });

EmployeeApp
	.join(EmployeesModel) // EmployeeApp.entities.employees
	.join(TasksModel)     // EmployeeApp.entities.tasks
	.join(OfficesModel);  // EmployeeApp.entities.tasks

Query Records

All tasks and employee information for a given employee

Fulfilling Requirement #1.

EmployeeApp.collections.assignements({employee: "CBaskin"}).go();

Returns the following:

{
	employees: [{
		employee: "cbaskin",
		firstName: "carol",
		lastName: "baskin",
		office: "big cat rescue",
		title: "owner",
		team: "cool cats and kittens",
		salary: "1,000,000",
		manager: "",
		dateHired: "1992-11-04",
		birthday: "1961-06-06",
	}].
	tasks: [{
		task: "Feed tigers",
		description: "Prepare food for tigers to eat",
		project: "Keep tigers alive",
		employee: "cbaskin"
	}, {
		task: "Fill water bowls",
		description: "Ensure the tigers have enough water",
		project: "Keep tigers alive",
		employee: "cbaskin"
	}]
}

Find all employees and office details for a given office

Fulfilling Requirement #2.

EmployeeApp.collections.workplaces({office: "big cat rescue"}).go()

Returns the following:

{
	employees: [{
		employee: "cbaskin",
		firstName: "carol",
		lastName: "baskin",
		office: "big cat rescue",
		title: "owner",
		team: "cool cats and kittens",
		salary: "1,000,000",
		manager: "",
		dateHired: "1992-11-04",
		birthday: "1961-06-06",
	}],
	offices: [{
		office: "big cat rescue",
		country: "usa",
		state: "florida",
		city: "tampa"
		zip: "12345"
		address: "123 Kitty Cat Lane"
	}]
}

Tasks for a given employee

Fulfilling Requirement #3.

EmployeeApp.entities.tasks.query.assigned({employee: "cbaskin"}).go();

Returns the following:

[
	{
		task: "Feed tigers",
		description: "Prepare food for tigers to eat",
		project: "Keep tigers alive",
		employee: "cbaskin"
	}, {
		task: "Fill water bowls",
		description: "Ensure the tigers have enough water",
		project: "Keep tigers alive",
		employee: "cbaskin"
	}
]

Tasks for a given project

Fulfilling Requirement #4.

EmployeeApp.entities.tasks.query.project({project: "Murder Carol"}).go();

Returns the following:

[
	{
		task: "Hire hitman",
		description: "Find someone to murder Carol",
		project: "Murder Carol",
		employee: "jexotic"
	}
];

Find office locations

Fulfilling Requirement #5.

EmployeeApp.entities.office.locations({country: "usa", state: "florida"}).go()

Returns the following:

[
	{
		office: "big cat rescue",
		country: "usa",
		state: "florida",
		city: "tampa"
		zip: "12345"
		address: "123 Kitty Cat Lane"
	}
]

Find employee salaries and titles

Fulfilling Requirement #6.

EmployeeApp.entities.employees
	.roles({title: "animal wrangler"})
	.lte({salary: "150.00"})
	.go()

Returns the following:

[
	{
		employee: "ssaffery",
		firstName: "saff",
		lastName: "saffery",
		office: "gw zoo",
		title: "animal wrangler",
		team: "keepers",
		salary: "105.00",
		manager: "jexotic",
		dateHired: "1999-02-23",
		birthday: "1960-07-11",
	}
]

Find employee birthdays or anniversaries

Fulfilling Requirement #7.

EmployeeApp.entities.employees
	.workplaces({office: "gw zoo"})
	.upcomingCelebrations("2020-05-01", "2020-06-01")
	.go()

Returns the following:

[
	{
		employee: "jexotic",
		firstName: "joe",
		lastName: "maldonado-passage",
		office: "gw zoo",
		title: "tiger king",
		team: "founders",
		salary: "10000.00",
		manager: "jlowe",
		dateHired: "1999-02-23",
		birthday: "1963-03-05",
	}
]

Find direct reports

Fulfilling Requirement #8.

EmployeeApp.entities.employees
	.reports({manager: "jlowe"})
	.go()

Returns the following:

[
	{
		employee: "jexotic",
		firstName: "joe",
		lastName: "maldonado-passage",
		office: "gw zoo",
		title: "tiger king",
		team: "founders",
		salary: "10000.00",
		manager: "jlowe",
		dateHired: "1999-02-23",
		birthday: "1963-03-05",
	}
]

Shopping Mall Property Management App

For an example, lets look at the needs of application used to manage Shopping Mall properties. The application assists employees in the day-to-day operations of multiple Shopping Malls.

Shopping Mall Requirements

1. As a Maintenance Worker I need to know which stores are currently in each Mall down to the Building they are located.
2. As a Helpdesk Employee I need to locate related stores in Mall locations by Store Category.
3. As a Property Manager I need to identify upcoming leases in need of renewal.

Create a new Entity using the StoreLocations schema defined above

const DynamoDB = require("aws-sdk/clients/dynamodb");
const client = new DynamoDB.DocumentClient();
const StoreLocations = new Entity(model, {client, table: "StoreLocations"});

Access Patterns are accessible on the StoreLocation

PUT Record

Add a new Store to the Mall

await StoreLocations.create({
	mallId: "EastPointe",
	storeId: "LatteLarrys",
	buildingId: "BuildingA1",
	unitId: "B47",
	category: "spite store",
	leaseEndDate: "2020-02-29",
	rent: "5000.00",
}).go();

Returns the following:

{
	"mallId": "EastPointe",
	"storeId": "LatteLarrys",
	"buildingId": "BuildingA1",
	"unitId": "B47",
	"category": "spite store",
	"leaseEndDate": "2020-02-29",
	"rent": "5000.00",
	"discount": "0.00",
}

---

UPDATE Record

Change the Store's Lease Date

When updating a record, you must include all Facets associated with the table's primary PK and SK.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
await StoreLocations.update({storeId, mallId, buildingId, unitId}).set({
	leaseEndDate: "2021-02-28"
}).go();

Returns the following:

{
	"leaseEndDate": "2021-02-28"
}

GET Record

Retrieve a specific Store in a Mall

When retrieving a specific record, you must include all Facets associated with the table's primary PK and SK.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
await StoreLocations.get({storeId, mallId, buildingId, unitId}).go();

Returns the following:

{
	"mallId": "EastPointe",
	"storeId": "LatteLarrys",
	"buildingId": "BuildingA1",
	"unitId": "B47",
	"category": "spite store",
	"leaseEndDate": "2021-02-28",
	"rent": "5000.00",
	"discount": "0.00"
}

DELETE Record

Remove a Store location from the Mall

When removing a specific record, you must include all Facets associated with the table's primary PK and SK.

let storeId = "LatteLarrys";
let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let storeId = "LatteLarrys";
await StoreLocations.delete({storeId, mallId, buildingId, unitId}).go();

Returns the following:

{}

Query Records

All Stores in a particular mall

Fulfilling Requirement #1.

let mallId = "EastPointe";
let stores = await StoreLocations.malls({mallId}).query().go();

All Stores in a particular mall building

Fulfilling Requirement #1.

let mallId = "EastPointe";
let buildingId = "BuildingA1";
let stores = await StoreLocations.malls({mallId}).query({buildingId}).go();

Find the store located in unit B47

Fulfilling Requirement #1.

let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let stores = await StoreLocations.malls({mallId}).query({buildingId, unitId}).go();

Stores by Category at Mall

Fulfilling Requirement #2.

let mallId = "EastPointe";
let category = "food/coffee";
let stores = await StoreLocations.malls({mallId}).byCategory(category).go();

Stores by upcoming lease

Fulfilling Requirement #3.

let mallId = "EastPointe";
let q2StartDate = "2020-04-01";
let stores = await StoreLocations.leases({mallId}).lt({leaseEndDate: q2StateDate}).go();

Stores will renewals for Q4

Fulfilling Requirement #3.

let mallId = "EastPointe";
let q4StartDate = "2020-10-01";
let q4EndDate = "2020-12-31";
let stores = await StoreLocations.leases(mallId)
    .between (
      {leaseEndDate: q4StartDate}, 
      {leaseEndDate: q4EndDate})
    .go();

Spite-stores with release renewals this year

Fulfilling Requirement #3.

let mallId = "EastPointe";
let yearStarDate = "2020-01-01";
let yearEndDate = "2020-12-31";
let storeId = "LatteLarrys";
let stores = await StoreLocations.leases(mallId)
    .between (
      {leaseEndDate: yearStarDate}, 
      {leaseEndDate: yearEndDate})
    .filter(attr => attr.category.eq("Spite Store"))
    .go();

All Latte Larrys in a particular mall building

let mallId = "EastPointe";
let buildingId = "BuildingA1";
let unitId = "B47";
let storeId = "LatteLarrys";
let stores = await StoreLocations.malls({mallId}).query({buildingId, storeId}).go();

Version 1 Migration

This section is to detail any breaking changes made on the journey to a stable 1.0 product.

New schema format/breaking key format change

It became clear when I added the concept of a Service that the "version" paradigm of having the version in the PK wasnt going to work. This is because collection queries use the same PK for all entities and this would prevent some entities in a Service to change versions without impacting the service as a whole. The better more is the place the version in the SK after the entity name so that all version of an entity can be queried. This will work nicely into the migration feature I have planned that will help migrate between model versions.

To address this change, I decide it would be best to change the structure for defining a model, which is then used as heuristic to determine where to place the version in the key (PK or SK). This has the benefit of not breaking existing models, but does increase some complexity in the underlying code.

Additionally a change was made to the Service class. New Services would take a string of the service name instead of an object as before.

In the old scheme, version came after the service name (see ^).

pk: $mallstoredirectory_1#mall_eastpointe
                        ^
sk: $mallstores#building_buildinga#store_lattelarrys

In the new scheme, version comes after the entity name (see ^).

pk: $mallstoredirectory#mall_eastpointe

sk: $mallstores_1#building_buildinga#store_lattelarrys
                ^

In practice the change looks like this for use of Entity:

const  DynamoDB  =  require("aws-sdk/clients/dynamodb");
const {Entity} = require("electrodb");
const client = new DynamoDB.DocumentClient();
const table = "dynamodb_table_name";

// old way
let old_schema = {
  entity: "model_name",
  service: "service_name",
  version: "1",
  table: table,
  attributes: {},
  indexes: {}
};
new Entity(old_schema, {client});

// new way
let new_schema = {
  model: {
    entity: "model_name",
    service: "service_name",
    version: "1",
  },
  attributes: {},
  indexes: {}
};
new Entity(new_schema, {client, table});

And changes to usage of Service would look like this:

const  DynamoDB  =  require("aws-sdk/clients/dynamodb");
const {Service} = require("electrodb");
const client = new DynamoDB.DocumentClient();
const table = "dynamodb_table_name";

// old way
new Service({
  service: "service_name",
  version: "1",
  table: table,
}, {client});

// new way
new Service("service_name", {client, table});

Coming Soon

• Default query options defined on the model to give more general control of interactions with the Entity.
• Append/Add/Subtract/Remove updates capabilities
• Complex attributes (list, map, set)
• Data migration capabilities
• TypeScript type definition generation