Example program for the new SetTrace()
Does INSERT, then SELECT on the inserted rows (in-memory database). The purpose of all these is to cause activity so there will be trace messages to display. Trace message formatting is included (a useful format, with explanations).type
A.N
Yasuhiro Matsumoto
parent
2b0a8971e3
commit
17a684694a
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@ -0,0 +1,264 @@
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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/gimpldo/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: uint(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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