SQLite

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains the implementation of the sqlite3_prepare()
** interface, and routines that contribute to loading the database schema
** from disk.
**
** $Id: prepare.c,v 1.110 2009/03/19 07:58:31 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** Fill the InitData structure with an error message that indicates
** that the database is corrupt.
*/

  sqlite3BtreeLeaveAll(db);
  sqlite3_mutex_leave(db->mutex);
  return rc;
}

/*
** Rerun the compilation of a statement after a schema change.
**
** If the statement is successfully recompiled, return SQLITE_OK. Otherwise,
** if the statement cannot be recompiled because another connection has
** locked the sqlite3_master table, return SQLITE_LOCKED. If any other error
** occurs, return SQLITE_SCHEMA.
*/
int sqlite3Reprepare(Vdbe *p){
  int rc;
  sqlite3_stmt *pNew;
  const char *zSql;
  sqlite3 *db;

  assert( sqlite3_mutex_held(sqlite3VdbeDb(p)->mutex) );
  zSql = sqlite3_sql((sqlite3_stmt *)p);
  assert( zSql!=0 );  /* Reprepare only called for prepare_v2() statements */
  db = sqlite3VdbeDb(p);
  assert( sqlite3_mutex_held(db->mutex) );
  rc = sqlite3LockAndPrepare(db, zSql, -1, 0, &pNew, 0);
  if( rc ){
    if( rc==SQLITE_NOMEM ){
      db->mallocFailed = 1;
    }
    assert( pNew==0 );
    return (rc==SQLITE_LOCKED) ? SQLITE_LOCKED : SQLITE_SCHEMA;
  }else{
    assert( pNew!=0 );
  }
  sqlite3VdbeSwap((Vdbe*)pNew, p);
  sqlite3TransferBindings(pNew, (sqlite3_stmt*)p);
  sqlite3VdbeResetStepResult((Vdbe*)pNew);
  sqlite3VdbeFinalize((Vdbe*)pNew);
  return SQLITE_OK;
}


/*
** Two versions of the official API.  Legacy and new use.  In the legacy
** version, the original SQL text is not saved in the prepared statement
** and so if a schema change occurs, SQLITE_SCHEMA is returned by

**
*************************************************************************
**
** This file contains the implementation of some Tcl commands used to
** test that sqlite3 database handles may be concurrently accessed by 
** multiple threads. Right now this only works on unix.
**
** $Id: test_thread.c,v 1.12 2009/03/19 07:58:31 danielk1977 Exp $
*/

#include "sqliteInt.h"
#include <tcl.h>

#if SQLITE_THREADSAFE

  char *zScript;           /* The script to execute. */
  Tcl_Interp *interp;      /* The interpreter to execute it in. */
};

static Tcl_ObjCmdProc sqlthread_proc;
static Tcl_ObjCmdProc clock_seconds_proc;
static Tcl_ObjCmdProc blocking_step_proc;
static Tcl_ObjCmdProc blocking_prepare_v2_proc;
int Sqlitetest1_Init(Tcl_Interp *);

/* Functions from test1.c */
void *sqlite3TestTextToPtr(const char *);
const char *sqlite3TestErrorName(int);
int getDbPointer(Tcl_Interp *, const char *, sqlite3 **);
int sqlite3TestMakePointerStr(Tcl_Interp *, char *, void *);
int sqlite3TestErrCode(Tcl_Interp *, sqlite3 *, int);

/*
** Handler for events of type EvalEvent.
*/
static int tclScriptEvent(Tcl_Event *evPtr, int flags){
  int rc;
  EvalEvent *p = (EvalEvent *)evPtr;
  rc = Tcl_Eval(p->interp, p->zScript);

  extern int Sqlitetest_mutex_Init(Tcl_Interp*);

  interp = Tcl_CreateInterp();
  Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
  Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, pSqlThread, 0);
#if defined(OS_UNIX) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
  Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
  Tcl_CreateObjCommand(
      interp, "sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc,0,0);
#endif
  Sqlitetest1_Init(interp);
  Sqlitetest_mutex_Init(interp);

  rc = Tcl_Eval(interp, p->zScript);
  pRes = Tcl_GetObjResult(interp);
  pList = Tcl_NewObj();

  pthread_cond_t cond;                 /* Condition variable to wait on */
  pthread_mutex_t mutex;               /* Mutex to protect structure */
};

/*
** This function is an unlock-notify callback registered with SQLite.
*/
static void unlock_notify_cb(void **apArg, int nArg){
  int i;
  for(i=0; i<nArg; i++){
    UnlockNotification *p = (UnlockNotification *)apArg[i];
    pthread_mutex_lock(&p->mutex);
    p->fired = 1;
    pthread_cond_signal(&p->cond);
    pthread_mutex_unlock(&p->mutex);
  }
}

/*
** This function assumes that an SQLite API call (either sqlite3_prepare_v2() 
** or sqlite3_step()) has just returned SQLITE_LOCKED. The argument is the
** associated database connection.
**
** This function calls sqlite3_unlock_notify() to register for an 
** unlock-notify callback, then blocks until that callback is delivered 
** and returns SQLITE_OK. The caller should then retry the failed operation.
**
** Or, if sqlite3_unlock_notify() indicates that to block would deadlock 
** the system, then this function returns SQLITE_LOCKED immediately. In 
** this case the caller should not retry the operation and should roll 
** back the current transaction (if any).
*/
static int wait_for_unlock_notify(sqlite3 *db){
  int rc;
  UnlockNotification un;

  /* Initialize the UnlockNotification structure. */
  un.fired = 0;
  pthread_mutex_init(&un.mutex, 0);
  pthread_cond_init(&un.cond, 0);

  /* Register for an unlock-notify callback. */
  rc = sqlite3_unlock_notify(db, unlock_notify_cb, (void *)&un);
  assert( rc==SQLITE_LOCKED || rc==SQLITE_OK );

  /* The call to sqlite3_unlock_notify() always returns either SQLITE_LOCKED 
  ** or SQLITE_OK. 
  **
  ** If SQLITE_LOCKED was returned, then the system is deadlocked. In this
  ** case this function needs to return SQLITE_LOCKED to the caller so 
  ** that the current transaction can be rolled back. Otherwise, block
  ** until the unlock-notify callback is invoked, then return SQLITE_OK.
  */
  if( rc==SQLITE_OK ){
    pthread_mutex_lock(&un.mutex);
    if( !un.fired ){
      pthread_cond_wait(&un.cond, &un.mutex);
    }
    pthread_mutex_unlock(&un.mutex);
  }

  /* Destroy the mutex and condition variables. */
  pthread_cond_destroy(&un.cond);
  pthread_mutex_destroy(&un.mutex);

  return rc;
}

/*
** This function is a wrapper around the SQLite function sqlite3_step().
** It functions in the same way as step(), except that if a required
** shared-cache lock cannot be obtained, this function may block waiting for
** the lock to become available. In this scenario the normal API step()
** function always returns SQLITE_LOCKED.
**
** If this function returns SQLITE_LOCKED, the caller should rollback
** the current transaction (if any) and try again later. Otherwise, the
** system may become deadlocked.
*/
int sqlite3_blocking_step(sqlite3_stmt *pStmt){
  int rc;

  while( SQLITE_LOCKED==(rc = sqlite3_step(pStmt)) ){
    rc = wait_for_unlock_notify(sqlite3_db_handle(pStmt));

    if( rc!=SQLITE_OK ) break;

    sqlite3_reset(pStmt);


  }

  return rc;
}











/*
** This function is a wrapper around the SQLite function sqlite3_prepare_v2().
** It functions in the same way as prepare_v2(), except that if a required
** shared-cache lock cannot be obtained, this function may block waiting for
** the lock to become available. In this scenario the normal API prepare_v2()
** function always returns SQLITE_LOCKED.
**
** If this function returns SQLITE_LOCKED, the caller should rollback
** the current transaction (if any) and try again later. Otherwise, the
** system may become deadlocked.


*/

int sqlite3_blocking_prepare_v2(

  sqlite3 *db,              /* Database handle. */
  const char *zSql,         /* UTF-8 encoded SQL statement. */
  int nSql,                 /* Length of zSql in bytes. */
  sqlite3_stmt **ppStmt,    /* OUT: A pointer to the prepared statement */
  const char **pz           /* OUT: End of parsed string */
){


  int rc;
  while( SQLITE_LOCKED==(rc = sqlite3_prepare_v2(db, zSql, nSql, ppStmt, pz)) ){
    rc = wait_for_unlock_notify(db);

    if( rc!=SQLITE_OK ) break;




  }

  return rc;
}
/* END_SQLITE_BLOCKING_STEP */

/*
** Usage: sqlite3_blocking_step STMT
**
** Advance the statement to the next row.
*/
static int blocking_step_proc(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){




  sqlite3_stmt *pStmt;
  int rc;

  if( objc!=2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "STMT");
    return TCL_ERROR;
  }

  pStmt = (sqlite3_stmt*)sqlite3TestTextToPtr(Tcl_GetString(objv[1]));
  rc = sqlite3_blocking_step(pStmt);

  Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), 0);
  return TCL_OK;
}

/*
** Usage: sqlite3_blocking_prepare_v2 DB sql bytes ?tailvar?
*/
static int blocking_prepare_v2_proc(
  void * clientData,
  Tcl_Interp *interp,
  int objc,
  Tcl_Obj *CONST objv[]
){
  sqlite3 *db;
  const char *zSql;
  int bytes;
  const char *zTail = 0;
  sqlite3_stmt *pStmt = 0;
  char zBuf[50];
  int rc;

  if( objc!=5 && objc!=4 ){
    Tcl_AppendResult(interp, "wrong # args: should be \"", 
       Tcl_GetString(objv[0]), " DB sql bytes tailvar", 0);
    return TCL_ERROR;
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) ) return TCL_ERROR;
  zSql = Tcl_GetString(objv[2]);
  if( Tcl_GetIntFromObj(interp, objv[3], &bytes) ) return TCL_ERROR;

  rc = sqlite3_blocking_prepare_v2(db, zSql, bytes, &pStmt, objc>=5?&zTail : 0);
  assert(rc==SQLITE_OK || pStmt==0);
  if( zTail && objc>=5 ){
    if( bytes>=0 ){
      bytes = bytes - (zTail-zSql);
    }
    Tcl_ObjSetVar2(interp, objv[4], 0, Tcl_NewStringObj(zTail, bytes), 0);
  }
  if( rc!=SQLITE_OK ){
    assert( pStmt==0 );
    sprintf(zBuf, "%s ", (char *)sqlite3TestErrorName(rc));
    Tcl_AppendResult(interp, zBuf, sqlite3_errmsg(db), 0);
    return TCL_ERROR;
  }

  if( pStmt ){
    if( sqlite3TestMakePointerStr(interp, zBuf, pStmt) ) return TCL_ERROR;
    Tcl_AppendResult(interp, zBuf, 0);
  }
  return TCL_OK;
}

#endif
/*
** End of implementation of [sqlite3_blocking_step].
************************************************************************/

/*
** Register commands with the TCL interpreter.
*/
int SqlitetestThread_Init(Tcl_Interp *interp){
  Tcl_CreateObjCommand(interp, "sqlthread", sqlthread_proc, 0, 0);
  Tcl_CreateObjCommand(interp, "clock_seconds", clock_seconds_proc, 0, 0);
#if defined(OS_UNIX) && defined(SQLITE_ENABLE_UNLOCK_NOTIFY)
  Tcl_CreateObjCommand(interp, "sqlite3_blocking_step", blocking_step_proc,0,0);
  Tcl_CreateObjCommand(
      interp, "sqlite3_blocking_prepare_v2", blocking_prepare_v2_proc,0,0);
#endif
  return TCL_OK;
}
#else
int SqlitetestThread_Init(Tcl_Interp *interp){
  return TCL_OK;
}
#endif

**    May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file contains code use to implement APIs that are part of the
** VDBE.
**
** $Id: vdbeapi.c,v 1.154 2009/03/19 07:58:31 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "vdbeInt.h"

#if 0 && defined(SQLITE_ENABLE_MEMORY_MANAGEMENT)
/*
** The following structure contains pointers to the end points of a

  if( pStmt ){
    int cnt = 0;
    Vdbe *v = (Vdbe*)pStmt;
    sqlite3 *db = v->db;
    sqlite3_mutex_enter(db->mutex);
    while( (rc = sqlite3Step(v))==SQLITE_SCHEMA
           && cnt++ < 5
           && (rc = vdbeReprepare(v))==SQLITE_OK ){
      sqlite3_reset(pStmt);
      v->expired = 0;
    }
    if( rc==SQLITE_SCHEMA && v->isPrepareV2 && db->pErr ){
      /* This case occurs after failing to recompile an sql statement. 
      ** The error message from the SQL compiler has already been loaded 
      ** into the database handle. This block copies the error message 

# 2009 March 04
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# $Id: notify2.test,v 1.2 2009/03/19 07:58:31 danielk1977 Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

# The tests in this file test the sqlite3_blocking_step() function in
# test_thread.c. sqlite3_blocking_step() is not an SQLite API function,
# it is just a demonstration of how the sqlite3_unlock_notify() function

  # Proc used by threads to execute SQL.
  #
  proc execsql_blocking {db zSql} {
    set lRes [list]
    set rc SQLITE_OK

    while {$rc=="SQLITE_OK" && $zSql ne ""} {
      set STMT [$::xPrepare $db $zSql -1 zSql]
      while {[set rc [$::xStep $STMT]] eq "SQLITE_ROW"} {
        for {set i 0} {$i < [sqlite3_column_count $STMT]} {incr i} {
          lappend lRes [sqlite3_column_text $STMT 0]
        }
      }
      set rc [sqlite3_finalize $STMT]
    }

    # Each transaction does 3 operations. Each operation is either a read
    # or write of a randomly selected table (t1, t2 or t3). Set the variables
    # $SQL(1), $SQL(2) and $SQL(3) to the SQL commands used to implement
    # each operation.
    #
    for {set ii 1} {$ii <= 3} {incr ii} {
      foreach {tbl database} [select_one {t1 main} {t2 aux2} {t3 aux3}] {}

      set SQL($ii) [string map [list xxx $tbl yyy $database] [select_one {
            SELECT 
              (SELECT b FROM xxx WHERE a=(SELECT max(a) FROM xxx))==total(a) 
              FROM xxx WHERE a!=(SELECT max(a) FROM xxx);
      } {
            DELETE FROM xxx WHERE a<(SELECT max(a)-100 FROM xxx);
            INSERT INTO xxx SELECT NULL, total(a) FROM xxx;
      } 
#      {
#            CREATE INDEX IF NOT EXISTS yyy.xxx_i ON xxx(b);
#      } {
#            DROP INDEX IF EXISTS yyy.xxx_i;
#      }
      ]]
    }

    # Execute the SQL transaction.
    #
    set rc [catch { execsql_blocking $::DB "
        BEGIN;
          $SQL(1);

  # Close the database connection and return 0.
  #
  sqlite3_close $::DB
  expr 0
}

foreach {iTest xStep xPrepare} {
  1 sqlite3_blocking_step sqlite3_blocking_prepare_v2
  2 sqlite3_step          sqlite3_prepare_v2
} {
  file delete -force test.db test2.db test3.db

  set ThreadSetup "set xStep $xStep;set xPrepare $xPrepare;set nSecond $nSecond"

  # Set up the database schema used by this test. Each thread opens file
  # test.db as the main database, then attaches files test2.db and test3.db
  # as auxillary databases. Each file contains a single table (t1, t2 and t3, in
  # files test.db, test2.db and test3.db, respectively). 
  #
  do_test notify2-$iTest.1.1 {