Create main.go
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src/github.com/mattn/go-sqlite3/_example/trace/main.go
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264
src/github.com/mattn/go-sqlite3/_example/trace/main.go
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package main
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import (
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"database/sql"
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"fmt"
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"log"
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"os"
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sqlite3 "github.com/mattn/go-sqlite3"
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)
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func traceCallback(info sqlite3.TraceInfo) int {
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// Not very readable but may be useful; uncomment next line in case of doubt:
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//fmt.Printf("Trace: %#v\n", info)
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var dbErrText string
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if info.DBError.Code != 0 || info.DBError.ExtendedCode != 0 {
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dbErrText = fmt.Sprintf("; DB error: %#v", info.DBError)
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} else {
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dbErrText = "."
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}
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// Show the Statement-or-Trigger text in curly braces ('{', '}')
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// since from the *paired* ASCII characters they are
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// the least used in SQL syntax, therefore better visual delimiters.
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// Maybe show 'ExpandedSQL' the same way as 'StmtOrTrigger'.
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//
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// A known use of curly braces (outside strings) is
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// for ODBC escape sequences. Not likely to appear here.
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//
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// Template languages, etc. don't matter, we should see their *result*
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// at *this* level.
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// Strange curly braces in SQL code that reached the database driver
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// suggest that there is a bug in the application.
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// The braces are likely to be either template syntax or
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// a programming language's string interpolation syntax.
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var expandedText string
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if info.ExpandedSQL != "" {
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if info.ExpandedSQL == info.StmtOrTrigger {
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expandedText = " = exp"
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} else {
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expandedText = fmt.Sprintf(" expanded {%q}", info.ExpandedSQL)
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}
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} else {
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expandedText = ""
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}
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// SQLite docs as of September 6, 2016: Tracing and Profiling Functions
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// https://www.sqlite.org/c3ref/profile.html
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//
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// The profile callback time is in units of nanoseconds, however
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// the current implementation is only capable of millisecond resolution
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// so the six least significant digits in the time are meaningless.
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// Future versions of SQLite might provide greater resolution on the profiler callback.
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var runTimeText string
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if info.RunTimeNanosec == 0 {
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if info.EventCode == sqlite3.TraceProfile {
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//runTimeText = "; no time" // seems confusing
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runTimeText = "; time 0" // no measurement unit
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} else {
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//runTimeText = "; no time" // seems useless and confusing
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}
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} else {
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const nanosPerMillisec = 1000000
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if info.RunTimeNanosec%nanosPerMillisec == 0 {
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runTimeText = fmt.Sprintf("; time %d ms", info.RunTimeNanosec/nanosPerMillisec)
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} else {
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// unexpected: better than millisecond resolution
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runTimeText = fmt.Sprintf("; time %d ns!!!", info.RunTimeNanosec)
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}
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}
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var modeText string
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if info.AutoCommit {
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modeText = "-AC-"
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} else {
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modeText = "+Tx+"
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}
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fmt.Printf("Trace: ev %d %s conn 0x%x, stmt 0x%x {%q}%s%s%s\n",
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info.EventCode, modeText, info.ConnHandle, info.StmtHandle,
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info.StmtOrTrigger, expandedText,
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runTimeText,
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dbErrText)
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return 0
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}
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func main() {
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eventMask := sqlite3.TraceStmt | sqlite3.TraceProfile | sqlite3.TraceRow | sqlite3.TraceClose
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sql.Register("sqlite3_tracing",
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&sqlite3.SQLiteDriver{
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ConnectHook: func(conn *sqlite3.SQLiteConn) error {
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err := conn.SetTrace(&sqlite3.TraceConfig{
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Callback: traceCallback,
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EventMask: eventMask,
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WantExpandedSQL: true,
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})
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return err
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},
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})
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os.Exit(dbMain())
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}
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// Harder to do DB work in main().
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// It's better with a separate function because
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// 'defer' and 'os.Exit' don't go well together.
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//
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// DO NOT use 'log.Fatal...' below: remember that it's equivalent to
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// Print() followed by a call to os.Exit(1) --- and
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// we want to avoid Exit() so 'defer' can do cleanup.
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// Use 'log.Panic...' instead.
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func dbMain() int {
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db, err := sql.Open("sqlite3_tracing", ":memory:")
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if err != nil {
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fmt.Printf("Failed to open database: %#+v\n", err)
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return 1
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}
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defer db.Close()
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err = db.Ping()
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if err != nil {
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log.Panic(err)
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}
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dbSetup(db)
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dbDoInsert(db)
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dbDoInsertPrepared(db)
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dbDoSelect(db)
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dbDoSelectPrepared(db)
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return 0
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}
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// 'DDL' stands for "Data Definition Language":
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// Note: "INTEGER PRIMARY KEY NOT NULL AUTOINCREMENT" causes the error
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// 'near "AUTOINCREMENT": syntax error'; without "NOT NULL" it works.
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const tableDDL = `CREATE TABLE t1 (
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id INTEGER PRIMARY KEY AUTOINCREMENT,
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note VARCHAR NOT NULL
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)`
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// 'DML' stands for "Data Manipulation Language":
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const insertDML = "INSERT INTO t1 (note) VALUES (?)"
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const selectDML = "SELECT id, note FROM t1 WHERE note LIKE ?"
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const textPrefix = "bla-1234567890-"
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const noteTextPattern = "%Prep%"
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const nGenRows = 4 // Number of Rows to Generate (for *each* approach tested)
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func dbSetup(db *sql.DB) {
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var err error
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_, err = db.Exec("DROP TABLE IF EXISTS t1")
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if err != nil {
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log.Panic(err)
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}
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_, err = db.Exec(tableDDL)
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if err != nil {
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log.Panic(err)
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}
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}
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func dbDoInsert(db *sql.DB) {
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const Descr = "DB-Exec"
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for i := 0; i < nGenRows; i++ {
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result, err := db.Exec(insertDML, textPrefix+Descr)
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if err != nil {
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log.Panic(err)
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}
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resultDoCheck(result, Descr, i)
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}
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}
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func dbDoInsertPrepared(db *sql.DB) {
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const Descr = "DB-Prepare"
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stmt, err := db.Prepare(insertDML)
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if err != nil {
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log.Panic(err)
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}
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defer stmt.Close()
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for i := 0; i < nGenRows; i++ {
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result, err := stmt.Exec(textPrefix + Descr)
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if err != nil {
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log.Panic(err)
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}
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resultDoCheck(result, Descr, i)
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}
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}
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func resultDoCheck(result sql.Result, callerDescr string, callIndex int) {
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lastID, err := result.LastInsertId()
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if err != nil {
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log.Panic(err)
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}
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nAffected, err := result.RowsAffected()
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if err != nil {
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log.Panic(err)
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}
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log.Printf("Exec result for %s (%d): ID = %d, affected = %d\n", callerDescr, callIndex, lastID, nAffected)
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}
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func dbDoSelect(db *sql.DB) {
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const Descr = "DB-Query"
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rows, err := db.Query(selectDML, noteTextPattern)
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if err != nil {
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log.Panic(err)
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}
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defer rows.Close()
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rowsDoFetch(rows, Descr)
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}
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func dbDoSelectPrepared(db *sql.DB) {
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const Descr = "DB-Prepare"
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stmt, err := db.Prepare(selectDML)
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if err != nil {
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log.Panic(err)
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}
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defer stmt.Close()
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rows, err := stmt.Query(noteTextPattern)
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if err != nil {
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log.Panic(err)
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}
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defer rows.Close()
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rowsDoFetch(rows, Descr)
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}
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func rowsDoFetch(rows *sql.Rows, callerDescr string) {
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var nRows int
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var id int64
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var note string
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for rows.Next() {
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err := rows.Scan(&id, ¬e)
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if err != nil {
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log.Panic(err)
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}
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log.Printf("Row for %s (%d): id=%d, note=%q\n",
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callerDescr, nRows, id, note)
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nRows++
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}
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if err := rows.Err(); err != nil {
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log.Panic(err)
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}
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log.Printf("Total %d rows for %s.\n", nRows, callerDescr)
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}
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