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dex/vendor/github.com/mattn/go-sqlite3/_example/trace/main.go
2016-10-03 12:48:25 -07:00

265 lines
6.2 KiB
Go

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