go-mysql-server

go-mysql-server is a SQL engine which parses standard SQL (based on MySQL syntax) and executes queries on data sources of your choice. A simple in-memory database and table implementation are provided, and you can query any data source you want by implementing a few interfaces.

go-mysql-server also provides a server implementation compatible with the MySQL wire protocol. That means it is compatible with MySQL ODBC, JDBC, or the default MySQL client shell interface.

Dolt, a SQL database with Git-style versioning, is the main database implementation of this package. Check out that project for reference implementations. Or, hop into the Dolt discord here if you want to talk to the core developers behind GMS.

Scope of this project

These are the goals of go-mysql-server:

• Be a generic extensible SQL engine that performs queries on your data sources.
• Provide a simple database implementation suitable for use in tests.
• Define interfaces you can implement to query your own data sources.
• Provide a runnable server speaking the MySQL wire protocol, connected to data sources of your choice.
• Optimize query plans.
• Allow implementors to add their own analysis steps and optimizations.
• Support indexed lookups and joins on data tables that support them.
• Support external index driver implementations such as pilosa.
• With few caveats and using a full database implementation, be a drop-in MySQL database replacement.

Non-goals of go-mysql-server:

• Be an application/server you can use directly.
• Provide any kind of backend implementation (other than the memory one used for testing) such as json, csv, yaml. That's for clients to implement and use.

What's the use case of go-mysql-server?

go-mysql-server has two primary uses case:

1. Stand-in for MySQL in a golang test environment, using the built-in memory database implementation.

2. Providing access to aribtrary data sources with SQL queries by implementing a handful of interfaces. The most complete real-world implementation is Dolt.

Installation

The import path for the package is github.com/dolthub/go-mysql-server.

To install it, run:

go get github.com/dolthub/go-mysql-server

Go Documentation

• go-mysql-server godoc

SQL syntax

The goal of go-mysql-server is to support 100% of the statements that MySQL does. We are continuously adding more functionality to the engine, but not everything is supported yet. To see what is currently included check the SUPPORTED file.

Third-party clients

We support and actively test against certain third-party clients to ensure compatibility between them and go-mysql-server. You can check out the list of supported third party clients in the SUPPORTED_CLIENTS file along with some examples on how to connect to go-mysql-server using them.

Available functions

Name	Description
ACOS	returns the arccos of an expression.
ASCII	returns the numeric value of the leftmost character.
ASIN	returns the arcsin of an expression.
ATAN	returs the arctan of an expression.
BIN	returns the binary representation of a number.
BIT_LENGTH	returns the data length of the argument in bits.
COS	returns the cosine of an expression.
COT	returns the arctangent of an expression.
CRC32	returns the cyclic redundancy check value of a given string as a 32-bit unsigned value.
DAYNAME	return the name of the weekday.
DEGREES	returns the number of degrees in the radian expression given.
FIRST_VALUE	value of argument from first row of window frame.
FROM_UNIXTIME	format Unix timestamp as a date.
HEX	returns the hexadecimal representation of the string or numeric value.
MD5	calculate MD5 checksum.
MICROSECOND	return the microseconds from argument.
MONTHNAME	return the name of the month.
PERCENT_RANK	percentage rank value.
RADIANS	returns the radian value of the degrees argument given.
ROW_NUMBER	the number of rows updated.
SHA1	calculate an SHA-1 160-bit checksum.
SHA1	calculate an SHA-1 160-bit checksum.
SHA2	calculate an SHA-2 checksum.
SIGN	return the sign of the argument.
SIN	returns the sine of the expression given.
TAN	returns the tangent of the expression given.
TIME_TO_SEC	return the argument converted to seconds.
UNHEX	return a string containing hex representation of a number.
WEEKOFYEAR	return the calendar week of the date (1-53).
ABS	returns the absolute value of an expression.
ARRAY_LENGTH	if the json representation is an array, this function returns its size.
AVG	returns the average value of expr in all rows.
BIN_TO_UUID	converts a binary UUID to a string UUID and returns the result. The one-argument form takes a binary UUID value. The UUID value is assumed not to have its time-low and time-high parts swapped. The string result is in the same order as the binary argument. The two-argument form takes a binary UUID value and a swap-flag value: If swap_flag is 0, the two-argument form is equivalent to the one-argument form. The string result is in the same order as the binary argument. If swap_flag is 1, the UUID value is assumed to have its time-low and time-high parts swapped. These parts are swapped back to their original position in the result value.
CEIL	returns the smallest integer value that is greater than or equal to number.
CEIL	returns the smallest integer value that is greater than or equal to number.
CHARACTER_LENGTH	returns the length of the string in characters.
CHARACTER_LENGTH	returns the length of the string in characters.
COALESCE	returns the first non-null value in a list.
CONCAT	concatenates any group of fields into a single string.
CONCAT_WS	concatenates any group of fields into a single string. The first argument is the separator for the rest of the arguments. The separator is added between the strings to be concatenated. The separator can be a string, as can the rest of the arguments. If the separator is NULL, the result is NULL.
CONNECTION_ID	return returns the current connection ID.
CONVERT_TZ	converts a datetime value dt from the time zone given by from_tz to the time zone given by to_tz and returns the resulting value.
COUNT	returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement.
CURDATE	return the current date.
CURRENT_DATE	return the current date.
CURRENT_TIME	return the current time.
CURRENT_TIMESTAMP	return the current date and time.
CURRENT_USER	returns the authenticated user name and host name.
CURTIME	return the current time.
DATABASE	return the default (current) database name.
DATABASE	return the default (current) database name.
DATE	returns the date part of the given date.
DATE_ADD	adds the interval to the given date.
DATE_FORMAT	format date as specified.
DATE_SUB	subtracts the interval from the given date.
DATETIME	returns a DATETIME value for the expression given (e.g. the string '2020-01-02').
DAY	returns the day of the month (0-31).
DAY	returns the day of the month (0-31).
DAYOFWEEK	returns the day of the week of the given date.
DAYOFYEAR	returns the day of the year of the given date.
EXPLODE	generates a new row in the result set for each element in the expressions provided.
FIRST	returns the first value in a sequence of elements of an aggregation.
FLOOR	returns the largest integer value that is less than or equal to number.
FORMAT	return a number formatted to specified number of decimal places.
FOUND_ROWS	for a SELECT with a LIMIT clause, the number of rows that would be returned were there no LIMIT clause.
FROM_BASE64	decodes the base64-encoded string str.
GET_LOCK	get a named lock.
GREATEST	returns the greatest numeric or string value.
GROUP_CONCAT	return a concatenated string.
HOUR	returns the hours of the given date.
IF	if expr1 evaluates to true, retuns expr2. Otherwise returns expr3.
IFNULL	if expr1 is not NULL, it returns expr1; otherwise it returns expr2.
INET6_ATON	return the numeric value of an IPv6 address.
INET6_NTOA	return the IPv6 address from a numeric value.
INET_ATON	return the numeric value of an IP address.
INET_NTOA	return the IP address from a numeric value.
INSTR	returns the 1-based index of the first occurence of str2 in str1, or 0 if it does not occur.
IS_BINARY	returns whether a blob is a binary file or not.
IS_FREE_LOCK	whether the named lock is free.
IS_IPV4	returns whether argument is an IPv4 address.
IS_IPV4_COMPAT	returns whether argument is an IPv4-compatible address.
IS_IPV4_MAPPED	returns whether argument is an IPv4-mapped address.
IS_IPV6	returns whether argument is an IPv6 address.
IS_USED_LOCK	whether the named lock is in use; return connection identifier if true.
IS_UUID	returns whether argument is a valid UUID.
ISNULL	returns whether a expr is null or not.
JSON_ARRAYAGG	return result set as a single JSON array.
JSON_CONTAINS	return whether JSON document contains specific object at path.
JSON_EXTRACT	return data from JSON document
JSON_OBJECT	create JSON object.
JSON_OBJECTAGG	return result set as a single JSON object.
JSON_UNQUOTE	unquotes JSON value and returns the result as a utf8mb4 string.
LAST	returns the last value in a sequence of elements of an aggregation.
LAST_INSERT_ID	value of the AUTOINCREMENT column for the last INSERT.
LEAST	returns the smaller numeric or string value.
LEFT	returns the first N characters in the string given.
LENGTH	returns the length of the string in bytes.
LN	returns the natural logarithm of X.
LOAD_FILE	returns a LoadFile object.
LOG	if called with one parameter, this function returns the natural logarithm of X. If called with two parameters, this function returns the logarithm of X to the base B. If X is less than or equal to 0, or if B is less than or equal to 1, then NULL is returned.
LOG10	returns the base-10 logarithm of X.
LOG2	returns the base-2 logarithm of X.
LOWER	returns the string str with all characters in lower case.
LOWER	returns the string str with all characters in lower case.
LPAD	returns the string str, left-padded with the string padstr to a length of len characters.
LTRIM	returns the string str with leading space characters removed.
MAX	returns the maximum value of expr in all rows.
MIN	returns the minimum value of expr in all rows.
MINUTE	returns the minutes of the given date.
MONTH	returns the month of the given date.
NOW	returns the current timestamp.
NULLIF	returns NULL if expr1 = expr2 is true, otherwise returns expr1.
POWER	returns the value of X raised to the power of Y.
POWER	returns the value of X raised to the power of Y.
RAND	returns a random number in the range 0 <= x < 1. If an argument is given, it is used to seed the random number generator.
REGEXP_LIKE	whether string matches regular expression.
REGEXP_REPLACE	replace substrings matching regular expression.
RELEASE_ALL_LOCKS	release all current named locks.
RELEASE_LOCK	release the named lock.
REPEAT	returns a string consisting of the string str repeated count times.
REPLACE	returns the string str with all occurrences of the string from_str replaced by the string to_str.
REVERSE	returns the string str with the order of the characters reversed.
RIGHT	return the specified rightmost number of characters.
ROUND	rounds the number to decimals decimal places.
ROW_COUNT	the number of rows updated.
RPAD	returns the string str, right-padded with the string padstr to a length of len characters.
RTRIM	returns the string str with trailing space characters removed.
SECOND	returns the seconds of the given date.
SLEEP	waits for the specified number of seconds (can be fractional).
SOUNDEX	returns the soundex of a string.
SPLIT	returns the parts of the string str split by the separator sep as a JSON array of strings.
SQRT	returns the square root of a nonnegative number X.
STR_TO_DATE	parses the date/datetime/timestamp expression according to the format specifier.
SUBSTRING	returns a substring from the provided string starting at pos with a length of len characters. If no len is provided, all characters from pos until the end will be taken.
SUBSTRING	returns a substring from the provided string starting at pos with a length of len characters. If no len is provided, all characters from pos until the end will be taken.
SUBSTRING	returns a substring from the provided string starting at pos with a length of len characters. If no len is provided, all characters from pos until the end will be taken.
SUBSTRING_INDEX	returns a substring after count appearances of delim. If count is negative, counts from the right side of the string.
SUM	returns the sum of expr in all rows.
TIMEDIFF	returns expr1 − expr2 expressed as a time value. expr1 and expr2 are time or date-and-time expressions, but both must be of the same type.
TIMESTAMP	returns a timestamp value for the expression given (e.g. the string '2020-01-02').
TO_BASE64	encodes the string str in base64 format.
UNIX_TIMESTAMP	returns the datetime argument to the number of seconds since the Unix epoch. With nor argument, returns the number of execonds since the Unix epoch for the current time.
UPPER	convert to uppercase.
UPPER	convert to uppercase.
USER	returns the authenticated user name and host name.
UTC_TIMESTAMP	returns the current UTC timestamp.
UUID	return a Universal Unique Identifier (UUID).
UUID_TO_BIN	convert string UUID to binary.
VALUES	define the values to be used during an INSERT.
WEEK	return the week number.
WEEKDAY	returns the weekday of the given date.
YEAR	returns the year of the given date.
YEARWEEK	returns year and week for a date. The year in the result may be different from the year in the date argument for the first and the last week of the year.

Configuration

The behaviour of certain parts of go-mysql-server can be configured using either environment variables or session variables.

Session variables are set using the following SQL queries:

SET <variable name> = <value>

Name	Type	Description
INMEMORY_JOINS	environment	If set it will perform all joins in memory. Default is off.
inmemory_joins	session	If set it will perform all joins in memory. Default is off. This has precedence over INMEMORY_JOINS.
MAX_MEMORY	environment	The maximum number of memory, in megabytes, that can be consumed by go-mysql-server. Any in-memory caches or computations will no longer try to use memory when the limit is reached. Note that this may cause certain queries to fail if there is not enough memory available, such as queries using DISTINCT, ORDER BY or GROUP BY with groupings.
DEBUG_ANALYZER	environment	If set, the analyzer will print debug messages. Default is off.

Example

go-mysql-server contains a SQL engine and server implementation. So, if you want to start a server, first instantiate the engine and pass your sql.Database implementation.

It will be in charge of handling all the logic to retrieve the data from your source. Here you can see an example using the in-memory database implementation:

package main

import (
	"time"

	sqle "github.com/dolthub/go-mysql-server"
	"github.com/dolthub/go-mysql-server/auth"
	"github.com/dolthub/go-mysql-server/memory"
	"github.com/dolthub/go-mysql-server/server"
	"github.com/dolthub/go-mysql-server/sql"
	"github.com/dolthub/go-mysql-server/sql/information_schema"
)

// Example of how to implement a MySQL server based on a Engine:
//
// ```
// > mysql --host=127.0.0.1 --port=3306 -u root mydb -e "SELECT * FROM mytable"
// +----------+-------------------+-------------------------------+---------------------+
// | name     | email             | phone_numbers                 | created_at          |
// +----------+-------------------+-------------------------------+---------------------+
// | John Doe | [email protected]      | ["555-555-555"]               | 2018-04-18 09:41:13 |
// | John Doe | [email protected]   | []                            | 2018-04-18 09:41:13 |
// | Jane Doe | [email protected]      | []                            | 2018-04-18 09:41:13 |
// | Evil Bob | [email protected] | ["555-666-555","666-666-666"] | 2018-04-18 09:41:13 |
// +----------+-------------------+-------------------------------+---------------------+
// ```
func main() {
	engine := sqle.NewDefault(
		sql.NewDatabaseProvider(
			createTestDatabase(),
			information_schema.NewInformationSchemaDatabase(),
		))

	config := server.Config{
		Protocol: "tcp",
		Address:  "localhost:3306",
		Auth:     auth.NewNativeSingle("root", "", auth.AllPermissions),
	}

	s, err := server.NewDefaultServer(config, engine)
	if err != nil {
		panic(err)
	}

	s.Start()
}

func createTestDatabase() *memory.Database {
	const (
		dbName    = "mydb"
		tableName = "mytable"
	)

	db := memory.NewDatabase(dbName)
	table := memory.NewTable(tableName, sql.Schema{
		{Name: "name", Type: sql.Text, Nullable: false, Source: tableName},
		{Name: "email", Type: sql.Text, Nullable: false, Source: tableName},
		{Name: "phone_numbers", Type: sql.JSON, Nullable: false, Source: tableName},
		{Name: "created_at", Type: sql.Timestamp, Nullable: false, Source: tableName},
	})

	db.AddTable(tableName, table)
	ctx := sql.NewEmptyContext()
	table.Insert(ctx, sql.NewRow("John Doe", "[email protected]", []string{"555-555-555"}, time.Now()))
	table.Insert(ctx, sql.NewRow("John Doe", "[email protected]", []string{}, time.Now()))
	table.Insert(ctx, sql.NewRow("Jane Doe", "[email protected]", []string{}, time.Now()))
	table.Insert(ctx, sql.NewRow("Evil Bob", "[email protected]", []string{"555-666-555", "666-666-666"}, time.Now()))
	return db
}

Then, you can connect to the server with any MySQL client:

> mysql --host=127.0.0.1 --port=3306 -u root mydb -e "SELECT * FROM mytable"
+----------+-------------------+-------------------------------+---------------------+
| name     | email             | phone_numbers                 | created_at          |
+----------+-------------------+-------------------------------+---------------------+
| John Doe | [email protected]      | ["555-555-555"]               | 2018-04-18 10:42:58 |
| John Doe | [email protected]   | []                            | 2018-04-18 10:42:58 |
| Jane Doe | [email protected]      | []                            | 2018-04-18 10:42:58 |
| Evil Bob | [email protected] | ["555-666-555","666-666-666"] | 2018-04-18 10:42:58 |
+----------+-------------------+-------------------------------+---------------------+

See the complete example here.

Queries examples

SELECT count(name) FROM mytable
+---------------------+
| COUNT(mytable.name) |
+---------------------+
|                   4 |
+---------------------+

SELECT name,year(created_at) FROM mytable
+----------+--------------------------+
| name     | YEAR(mytable.created_at) |
+----------+--------------------------+
| John Doe |                     2018 |
| John Doe |                     2018 |
| Jane Doe |                     2018 |
| Evil Bob |                     2018 |
+----------+--------------------------+

SELECT email FROM mytable WHERE name = 'Evil Bob'
+-------------------+
| email             |
+-------------------+
| [email protected] |
+-------------------+

Custom data source implementation

To create your own data source implementation you need to implement the following interfaces:

• sql.Database interface. This interface will provide tables from your data source. You can also implement other interfaces on your database to unlock additional functionality:

  • sql.TableCreator to support creating new tables
  • sql.TableDropper to support dropping tables
  • sql.TableRenamer to support renaming tables
  • sql.ViewCreator to support creating persisted views on your tables
  • sql.ViewDropper to support dropping persisted views

• sql.Table interface. This interface will provide rows of values from your data source. You can also implement other interfaces on your table to unlock additional functionality:

  • sql.InsertableTable to allow your data source to be updated with INSERT statements.
  • sql.UpdateableTable to allow your data source to be updated with UPDATE statements.
  • sql.DeletableTable to allow your data source to be updated with DELETE statements.
  • sql.ReplaceableTable to allow your data source to be updated with REPLACE statements.
  • sql.AlterableTable to allow your data source to have its schema modified by adding, dropping, and altering columns.
  • sql.IndexedTable to declare your table's native indexes to speed up query execution.
  • sql.IndexAlterableTable to accept the creation of new native indexes.
  • sql.ForeignKeyAlterableTable to signal your support of foreign key constraints in your table's schema and data.
  • sql.ProjectedTable to return rows that only contain a subset of the columns in the table. This can make query execution faster.
  • sql.FilteredTable to filter the rows returned by your table to those matching a given expression. This can make query execution faster (if your table implementation can filter rows more efficiently than checking an expression on every row in a table).

You can see a really simple data source implementation in the memory package.

Testing your data source implementation

go-mysql-server provides a suite of engine tests that you can use to validate that your implementation works as expected. See the enginetest package for details and examples.

Indexes

go-mysql-server exposes a series of interfaces to allow you to implement your own indexes so you can speed up your queries.

Native indexes

Tables can declare that they support native indexes, which means that they support efficiently returning a subset of their rows that match an expression. The memory package contains an example of this behavior, but please note that it is only for example purposes and doesn't actually make queries faster (although we could change this in the future).

Integrators should implement the sql.IndexedTable interface to declare which indexes their tables support and provide a means of returning a subset of the rows based on an sql.IndexLookup provided by their sql.Index implementation. There are a variety of extensions to sql.Index that can be implemented, each of which unlocks additional capabilities:

• sql.Index. Base-level interface, supporting equality lookups for an index.
• sql.AscendIndex. Adds support for > and >= indexed lookups.
• sql.DescendIndex. Adds support for < and <= indexed lookups.
• sql.NegateIndex. Adds support for negating other index lookups.
• sql.MergeableIndexLookup. Adds support for merging two sql.IndexLookups together to create a new one, representing AND and OR expressions on indexed columns.

Custom index driver implementation

Index drivers provide different backends for storing and querying indexes, without the need for a table to store and query its own native indexes. To implement a custom index driver you need to implement a few things:

• sql.IndexDriver interface, which will be the driver itself. Not that your driver must return an unique ID in the ID method. This ID is unique for your driver and should not clash with any other registered driver. It's the driver's responsibility to be fault tolerant and be able to automatically detect and recover from corruption in indexes.
• sql.Index interface, returned by your driver when an index is loaded or created.
• sql.IndexValueIter interface, which will be returned by your sql.IndexLookup and should return the values of the index.
• Don't forget to register the index driver in your sql.Context using context.RegisterIndexDriver(mydriver) to be able to use it.

To create indexes using your custom index driver you need to use extension syntax USING driverid on the index creation statement. For example:

CREATE INDEX foo ON table USING driverid (col1, col2)

go-mysql-server does not provide a production index driver implementation. We previously provided a pilosa implementation, but removed it due to the difficulty of supporting it on all platforms (pilosa doesn't work on Windows).

You can see an example of a driver implementation in the memory package.

Metrics

go-mysql-server utilizes github.com/go-kit/kit/metrics module to expose metrics (counters, gauges, histograms) for certain packages (so far for engine, analyzer, regex). If you already have metrics server (prometheus, statsd/statsite, influxdb, etc.) and you want to gather metrics also from go-mysql-server components, you will need to initialize some global variables by particular implementations to satisfy following interfaces:

// Counter describes a metric that accumulates values monotonically.
type Counter interface {
	With(labelValues ...string) Counter
	Add(delta float64)
}

// Gauge describes a metric that takes specific values over time.
type Gauge interface {
	With(labelValues ...string) Gauge
	Set(value float64)
	Add(delta float64)
}

// Histogram describes a metric that takes repeated observations of the same
// kind of thing, and produces a statistical summary of those observations,
// typically expressed as quantiles or buckets.
type Histogram interface {
	With(labelValues ...string) Histogram
	Observe(value float64)
}

You can use one of go-kit implementations or try your own. For instance, we want to expose metrics for prometheus server. So, before we start mysql engine, we have to set up the following variables:

import(
    "github.com/go-kit/kit/metrics/prometheus"
    promopts "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promhttp"
)

//....

// engine metrics
sqle.QueryCounter = prometheus.NewCounterFrom(promopts.CounterOpts{
		Namespace: "go_mysql_server",
		Subsystem: "engine",
		Name:      "query_counter",
	}, []string{
		"query",
	})
sqle.QueryErrorCounter = prometheus.NewCounterFrom(promopts.CounterOpts{
    Namespace: "go_mysql_server",
    Subsystem: "engine",
    Name:      "query_error_counter",
}, []string{
    "query",
    "error",
})
sqle.QueryHistogram = prometheus.NewHistogramFrom(promopts.HistogramOpts{
    Namespace: "go_mysql_server",
    Subsystem: "engine",
    Name:      "query_histogram",
}, []string{
    "query",
    "duration",
})

// analyzer metrics
analyzer.ParallelQueryCounter = prometheus.NewCounterFrom(promopts.CounterOpts{
    Namespace: "go_mysql_server",
    Subsystem: "analyzer",
    Name:      "parallel_query_counter",
}, []string{
    "parallelism",
})

// regex metrics
regex.CompileHistogram = prometheus.NewHistogramFrom(promopts.HistogramOpts{
    Namespace: "go_mysql_server",
    Subsystem: "regex",
    Name:      "compile_histogram",
}, []string{
    "regex",
    "duration",
})
regex.MatchHistogram = prometheus.NewHistogramFrom(promopts.HistogramOpts{
    Namespace: "go_mysql_server",
    Subsystem: "regex",
    Name:      "match_histogram",
}, []string{
    "string",
    "duration",
})

One important note - internally we set some labels for metrics, that's why have to pass those keys like "duration", "query", "driver", ... when we register metrics in prometheus. Other systems may have different requirements.

Powered by go-mysql-server

• dolt
• gitbase (defunct)

Acknowledgements

go-mysql-server was originally developed by the {source-d} organzation, and this repository was originally forked from src-d. We want to thank the entire {source-d} development team for their work on this project, especially Miguel Molina (@erizocosmico) and Juanjo Álvarez Martinez (@juanjux).

License

Apache License 2.0, see LICENSE