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sqlite3_trace.go
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sqlite3_trace.go
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// Copyright (C) 2019 Yasuhiro Matsumoto <[email protected]>.
//
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.
// +build sqlite_trace trace
package sqlite3
/*
#ifndef USE_LIBSQLITE3
#include <sqlite3-binding.h>
#else
#include <sqlite3.h>
#endif
#include <stdlib.h>
int traceCallbackTrampoline(unsigned int traceEventCode, void *ctx, void *p, void *x);
*/
import "C"
import (
"fmt"
"strings"
"sync"
"unsafe"
)
// Trace... constants identify the possible events causing callback invocation.
// Values are same as the corresponding SQLite Trace Event Codes.
const (
TraceStmt = uint32(C.SQLITE_TRACE_STMT)
TraceProfile = uint32(C.SQLITE_TRACE_PROFILE)
TraceRow = uint32(C.SQLITE_TRACE_ROW)
TraceClose = uint32(C.SQLITE_TRACE_CLOSE)
)
type TraceInfo struct {
// Pack together the shorter fields, to keep the struct smaller.
// On a 64-bit machine there would be padding
// between EventCode and ConnHandle; having AutoCommit here is "free":
EventCode uint32
AutoCommit bool
ConnHandle uintptr
// Usually filled, unless EventCode = TraceClose = SQLITE_TRACE_CLOSE:
// identifier for a prepared statement:
StmtHandle uintptr
// Two strings filled when EventCode = TraceStmt = SQLITE_TRACE_STMT:
// (1) either the unexpanded SQL text of the prepared statement, or
// an SQL comment that indicates the invocation of a trigger;
// (2) expanded SQL, if requested and if (1) is not an SQL comment.
StmtOrTrigger string
ExpandedSQL string // only if requested (TraceConfig.WantExpandedSQL = true)
// filled when EventCode = TraceProfile = SQLITE_TRACE_PROFILE:
// estimated number of nanoseconds that the prepared statement took to run:
RunTimeNanosec int64
DBError Error
}
// TraceUserCallback gives the signature for a trace function
// provided by the user (Go application programmer).
// SQLite 3.14 documentation (as of September 2, 2016)
// for SQL Trace Hook = sqlite3_trace_v2():
// The integer return value from the callback is currently ignored,
// though this may change in future releases. Callback implementations
// should return zero to ensure future compatibility.
type TraceUserCallback func(TraceInfo) int
type TraceConfig struct {
Callback TraceUserCallback
EventMask uint32
WantExpandedSQL bool
}
func fillDBError(dbErr *Error, db *C.sqlite3) {
// See SQLiteConn.lastError(), in file 'sqlite3.go' at the time of writing (Sept 5, 2016)
dbErr.Code = ErrNo(C.sqlite3_errcode(db))
dbErr.ExtendedCode = ErrNoExtended(C.sqlite3_extended_errcode(db))
dbErr.err = C.GoString(C.sqlite3_errmsg(db))
}
func fillExpandedSQL(info *TraceInfo, db *C.sqlite3, pStmt unsafe.Pointer) {
if pStmt == nil {
panic("No SQLite statement pointer in P arg of trace_v2 callback")
}
expSQLiteCStr := C.sqlite3_expanded_sql((*C.sqlite3_stmt)(pStmt))
defer C.sqlite3_free(unsafe.Pointer(expSQLiteCStr))
if expSQLiteCStr == nil {
fillDBError(&info.DBError, db)
return
}
info.ExpandedSQL = C.GoString(expSQLiteCStr)
}
//export traceCallbackTrampoline
func traceCallbackTrampoline(
traceEventCode C.uint,
// Parameter named 'C' in SQLite docs = Context given at registration:
ctx unsafe.Pointer,
// Parameter named 'P' in SQLite docs (Primary event data?):
p unsafe.Pointer,
// Parameter named 'X' in SQLite docs (eXtra event data?):
xValue unsafe.Pointer) C.int {
eventCode := uint32(traceEventCode)
if ctx == nil {
panic(fmt.Sprintf("No context (ev 0x%x)", traceEventCode))
}
contextDB := (*C.sqlite3)(ctx)
connHandle := uintptr(ctx)
var traceConf TraceConfig
var found bool
if eventCode == TraceClose {
// clean up traceMap: 'pop' means get and delete
traceConf, found = popTraceMapping(connHandle)
} else {
traceConf, found = lookupTraceMapping(connHandle)
}
if !found {
panic(fmt.Sprintf("Mapping not found for handle 0x%x (ev 0x%x)",
connHandle, eventCode))
}
var info TraceInfo
info.EventCode = eventCode
info.AutoCommit = (int(C.sqlite3_get_autocommit(contextDB)) != 0)
info.ConnHandle = connHandle
switch eventCode {
case TraceStmt:
info.StmtHandle = uintptr(p)
var xStr string
if xValue != nil {
xStr = C.GoString((*C.char)(xValue))
}
info.StmtOrTrigger = xStr
if !strings.HasPrefix(xStr, "--") {
// Not SQL comment, therefore the current event
// is not related to a trigger.
// The user might want to receive the expanded SQL;
// let's check:
if traceConf.WantExpandedSQL {
fillExpandedSQL(&info, contextDB, p)
}
}
case TraceProfile:
info.StmtHandle = uintptr(p)
if xValue == nil {
panic("NULL pointer in X arg of trace_v2 callback for SQLITE_TRACE_PROFILE event")
}
info.RunTimeNanosec = *(*int64)(xValue)
// sample the error //TODO: is it safe? is it useful?
fillDBError(&info.DBError, contextDB)
case TraceRow:
info.StmtHandle = uintptr(p)
case TraceClose:
handle := uintptr(p)
if handle != info.ConnHandle {
panic(fmt.Sprintf("Different conn handle 0x%x (expected 0x%x) in SQLITE_TRACE_CLOSE event.",
handle, info.ConnHandle))
}
default:
// Pass unsupported events to the user callback (if configured);
// let the user callback decide whether to panic or ignore them.
}
// Do not execute user callback when the event was not requested by user!
// Remember that the Close event is always selected when
// registering this callback trampoline with SQLite --- for cleanup.
// In the future there may be more events forced to "selected" in SQLite
// for the driver's needs.
if traceConf.EventMask&eventCode == 0 {
return 0
}
r := 0
if traceConf.Callback != nil {
r = traceConf.Callback(info)
}
return C.int(r)
}
type traceMapEntry struct {
config TraceConfig
}
var traceMapLock sync.Mutex
var traceMap = make(map[uintptr]traceMapEntry)
func addTraceMapping(connHandle uintptr, traceConf TraceConfig) {
traceMapLock.Lock()
defer traceMapLock.Unlock()
oldEntryCopy, found := traceMap[connHandle]
if found {
panic(fmt.Sprintf("Adding trace config %v: handle 0x%x already registered (%v).",
traceConf, connHandle, oldEntryCopy.config))
}
traceMap[connHandle] = traceMapEntry{config: traceConf}
}
func lookupTraceMapping(connHandle uintptr) (TraceConfig, bool) {
traceMapLock.Lock()
defer traceMapLock.Unlock()
entryCopy, found := traceMap[connHandle]
return entryCopy.config, found
}
// 'pop' = get and delete from map before returning the value to the caller
func popTraceMapping(connHandle uintptr) (TraceConfig, bool) {
traceMapLock.Lock()
defer traceMapLock.Unlock()
entryCopy, found := traceMap[connHandle]
if found {
delete(traceMap, connHandle)
}
return entryCopy.config, found
}
// SetTrace installs or removes the trace callback for the given database connection.
// It's not named 'RegisterTrace' because only one callback can be kept and called.
// Calling SetTrace a second time on same database connection
// overrides (cancels) any prior callback and all its settings:
// event mask, etc.
func (c *SQLiteConn) SetTrace(requested *TraceConfig) error {
connHandle := uintptr(unsafe.Pointer(c.db))
_, _ = popTraceMapping(connHandle)
if requested == nil {
// The traceMap entry was deleted already by popTraceMapping():
// can disable all events now, no need to watch for TraceClose.
err := c.setSQLiteTrace(0)
return err
}
reqCopy := *requested
// Disable potentially expensive operations
// if their result will not be used. We are doing this
// just in case the caller provided nonsensical input.
if reqCopy.EventMask&TraceStmt == 0 {
reqCopy.WantExpandedSQL = false
}
addTraceMapping(connHandle, reqCopy)
// The callback trampoline function does cleanup on Close event,
// regardless of the presence or absence of the user callback.
// Therefore it needs the Close event to be selected:
actualEventMask := uint(reqCopy.EventMask | TraceClose)
err := c.setSQLiteTrace(actualEventMask)
return err
}
func (c *SQLiteConn) setSQLiteTrace(sqliteEventMask uint) error {
rv := C.sqlite3_trace_v2(c.db,
C.uint(sqliteEventMask),
(*[0]byte)(unsafe.Pointer(C.traceCallbackTrampoline)),
unsafe.Pointer(c.db)) // Fourth arg is same as first: we are
// passing the database connection handle as callback context.
if rv != C.SQLITE_OK {
return c.lastError()
}
return nil
}