diff options
Diffstat (limited to '_example/trace/main.go')
| -rw-r--r-- | _example/trace/main.go | 264 |
1 files changed, 0 insertions, 264 deletions
diff --git a/_example/trace/main.go b/_example/trace/main.go deleted file mode 100644 index bef3d15..0000000 --- a/_example/trace/main.go +++ /dev/null @@ -1,264 +0,0 @@ -package main - -import ( - "database/sql" - "fmt" - "log" - "os" - - sqlite3 "github.com/mattn/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: 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, ¬e) - 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) -} |