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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Always enable exclusive access mode for TEMP databases. This cannot be changed. The locking_mode pragma has not effect on the TEMP database. (CVS 3766)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 04d3b9098ed06d5be24253edde50ea61b4641df8
User & Date: drh 2007-03-30 16:01:55
Context
2007-03-30
17:11
Coverage tests for some pragmas. (CVS 3767) check-in: eec7ab63 user: danielk1977 tags: trunk
16:01
Always enable exclusive access mode for TEMP databases. This cannot be changed. The locking_mode pragma has not effect on the TEMP database. (CVS 3766) check-in: 04d3b909 user: drh tags: trunk
14:56
Coverage improvements for where.c. (CVS 3765) check-in: df64894b user: danielk1977 tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/pager.c. 

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** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.308 2007/03/30 14:46:01 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
................................................................................
**                       Access is exclusive.  No other processes or
**                       threads can be reading or writing while one
**                       process is writing.
**
**   PAGER_SYNCED        The pager moves to this state from PAGER_EXCLUSIVE
**                       after all dirty pages have been written to the
**                       database file and the file has been synced to
**                       disk. All that remains to do is to remove the
**                       journal file and the transaction will be
**                       committed.
**
** The page cache comes up in PAGER_UNLOCK.  The first time a
** sqlite3PagerGet() occurs, the state transitions to PAGER_SHARED.
** After all pages have been released using sqlite_page_unref(),
** the state transitions back to PAGER_UNLOCK.  The first time
** that sqlite3PagerWrite() is called, the state transitions to
** PAGER_RESERVED.  (Note that sqlite_page_write() can only be
** called on an outstanding page which means that the pager must
** be in PAGER_SHARED before it transitions to PAGER_RESERVED.)

** The transition to PAGER_EXCLUSIVE occurs when before any changes
** are made to the database file.  After an sqlite3PagerRollback()
** or sqlite_pager_commit(), the state goes back to PAGER_SHARED.



*/
#define PAGER_UNLOCK      0
#define PAGER_SHARED      1   /* same as SHARED_LOCK */
#define PAGER_RESERVED    2   /* same as RESERVED_LOCK */
#define PAGER_EXCLUSIVE   4   /* same as EXCLUSIVE_LOCK */
#define PAGER_SYNCED      5

................................................................................
  /* pPager->nPage = 0; */
  /* pPager->nMaxPage = 0; */
  pPager->mxPage = 100;
  assert( PAGER_UNLOCK==0 );
  /* pPager->state = PAGER_UNLOCK; */
  /* pPager->errMask = 0; */
  pPager->tempFile = tempFile;




  pPager->memDb = memDb;
  pPager->readOnly = readOnly;
  /* pPager->needSync = 0; */
  pPager->noSync = pPager->tempFile || !useJournal;
  pPager->fullSync = (pPager->noSync?0:1);
  /* pPager->pFirst = 0; */
  /* pPager->pFirstSynced = 0; */
................................................................................
    /* This happens when the pager was in exclusive-access mode last
    ** time a (read or write) transaction was successfully concluded
    ** by this connection. Instead of deleting the journal file it was 
    ** kept open and truncated to 0 bytes.
    */
    assert( pPager->nRec==0 );
    assert( pPager->origDbSize==0 );

    sqlite3PagerPagecount(pPager);
    pPager->origDbSize = pPager->dbSize;
    pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
    if( !pPager->aInJournal ){
      rc = SQLITE_NOMEM;
    }else{

      rc = writeJournalHdr(pPager);
    }
  }
  assert( !pPager->journalOpen || pPager->journalOff>0 || rc!=SQLITE_OK );
  return rc;
}

................................................................................
** the locking-mode is set to the value specified.
**
** The returned value is either PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
** locking-mode.
*/
int sqlite3PagerLockingMode(Pager *pPager, int eMode){





  if( eMode>=0 ){
    pPager->exclusiveMode = eMode;
  }
  return (int)pPager->exclusiveMode;
}

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
/*








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** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.309 2007/03/30 16:01:55 drh Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>
................................................................................
**                       Access is exclusive.  No other processes or
**                       threads can be reading or writing while one
**                       process is writing.
**
**   PAGER_SYNCED        The pager moves to this state from PAGER_EXCLUSIVE
**                       after all dirty pages have been written to the
**                       database file and the file has been synced to
**                       disk. All that remains to do is to remove or
**                       truncate the journal file and the transaction 
**                       will be committed.
**
** The page cache comes up in PAGER_UNLOCK.  The first time a
** sqlite3PagerGet() occurs, the state transitions to PAGER_SHARED.
** After all pages have been released using sqlite_page_unref(),
** the state transitions back to PAGER_UNLOCK.  The first time
** that sqlite3PagerWrite() is called, the state transitions to
** PAGER_RESERVED.  (Note that sqlite3PagerWrite() can only be
** called on an outstanding page which means that the pager must
** be in PAGER_SHARED before it transitions to PAGER_RESERVED.)
** PAGER_RESERVED means that there is an open rollback journal.
** The transition to PAGER_EXCLUSIVE occurs before any changes
** are made to the database file, though writes to the rollback

** journal occurs with just PAGER_RESERVED.  After an sqlite3PagerRollback()
** or sqlite3PagerCommitPhaseTwo(), the state can go back to PAGER_SHARED,
** or it can stay at PAGER_EXCLUSIVE if we are in exclusive access mode.
*/
#define PAGER_UNLOCK      0
#define PAGER_SHARED      1   /* same as SHARED_LOCK */
#define PAGER_RESERVED    2   /* same as RESERVED_LOCK */
#define PAGER_EXCLUSIVE   4   /* same as EXCLUSIVE_LOCK */
#define PAGER_SYNCED      5

................................................................................
  /* pPager->nPage = 0; */
  /* pPager->nMaxPage = 0; */
  pPager->mxPage = 100;
  assert( PAGER_UNLOCK==0 );
  /* pPager->state = PAGER_UNLOCK; */
  /* pPager->errMask = 0; */
  pPager->tempFile = tempFile;
  assert( tempFile==PAGER_LOCKINGMODE_NORMAL 
          || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE );
  assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 );
  pPager->exclusiveMode = tempFile; 
  pPager->memDb = memDb;
  pPager->readOnly = readOnly;
  /* pPager->needSync = 0; */
  pPager->noSync = pPager->tempFile || !useJournal;
  pPager->fullSync = (pPager->noSync?0:1);
  /* pPager->pFirst = 0; */
  /* pPager->pFirstSynced = 0; */
................................................................................
    /* This happens when the pager was in exclusive-access mode last
    ** time a (read or write) transaction was successfully concluded
    ** by this connection. Instead of deleting the journal file it was 
    ** kept open and truncated to 0 bytes.
    */
    assert( pPager->nRec==0 );
    assert( pPager->origDbSize==0 );
    assert( pPager->aInJournal==0 );
    sqlite3PagerPagecount(pPager);

    pPager->aInJournal = sqliteMalloc( pPager->dbSize/8 + 1 );
    if( !pPager->aInJournal ){
      rc = SQLITE_NOMEM;
    }else{
      pPager->origDbSize = pPager->dbSize;
      rc = writeJournalHdr(pPager);
    }
  }
  assert( !pPager->journalOpen || pPager->journalOff>0 || rc!=SQLITE_OK );
  return rc;
}

................................................................................
** the locking-mode is set to the value specified.
**
** The returned value is either PAGER_LOCKINGMODE_NORMAL or
** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated)
** locking-mode.
*/
int sqlite3PagerLockingMode(Pager *pPager, int eMode){
  assert( eMode==PAGER_LOCKINGMODE_QUERY
            || eMode==PAGER_LOCKINGMODE_NORMAL
            || eMode==PAGER_LOCKINGMODE_EXCLUSIVE );
  assert( PAGER_LOCKINGMODE_QUERY<0 );
  assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 );
  if( eMode>=0 && !pPager->tempFile ){
    pPager->exclusiveMode = eMode;
  }
  return (int)pPager->exclusiveMode;
}

#if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
/*

Changes to test/exclusive.test. 

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#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library. The focus
# of these tests is exclusive access mode (i.e. the thing activated by 
# "PRAGMA locking_mode = EXCLUSIVE").
#
# $Id: exclusive.test,v 1.3 2007/03/26 10:27:19 danielk1977 Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
................................................................................
#----------------------------------------------------------------------
# Test cases exclusive-1.X test the PRAGMA logic.
#
do_test exclusive-1.0 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;

  } 
} {normal normal}
do_test exclusive-1.1 {
  execsql {
    pragma locking_mode = exclusive;
  } 
} {exclusive}
do_test exclusive-1.2 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;

  } 
} {exclusive exclusive}
do_test exclusive-1.3 {
  execsql {
    pragma locking_mode = normal;
  } 
} {normal}
do_test exclusive-1.4 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;

  } 
} {normal normal}
do_test exclusive-1.5 {
  execsql {
    pragma locking_mode = invalid;
  } 
} {normal}
do_test exclusive-1.6 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;

  } 
} {normal normal}
do_test exclusive-1.7 {
  execsql {
    pragma locking_mode = exclusive;
    ATTACH 'test2.db' as aux;
  }
  execsql {
    pragma main.locking_mode;
................................................................................
} {exclusive exclusive}
do_test exclusive-1.8 {
  execsql {
    pragma main.locking_mode = normal;
  }
  execsql {
    pragma main.locking_mode;

    pragma aux.locking_mode;
  }
} {normal exclusive}
do_test exclusive-1.9 {
  execsql {
    pragma locking_mode;
  }
} {exclusive}
do_test exclusive-1.10 {
  execsql {
................................................................................
} {normal normal exclusive}
do_test exclusive-1.12 {
  execsql {
    pragma locking_mode = normal;
  }
  execsql {
    pragma main.locking_mode;

    pragma aux.locking_mode;
    pragma aux2.locking_mode;
  }
} {normal normal normal}
do_test exclusive-1.13 {
  execsql {
    ATTACH 'test4.db' as aux3;
  }
  execsql {
    pragma main.locking_mode;

    pragma aux.locking_mode;
    pragma aux2.locking_mode;
    pragma aux3.locking_mode;
  }
} {normal normal normal normal}

do_test exclusive-1.99 {
  execsql {
    DETACH aux;
    DETACH aux2;
    DETACH aux3;
  }
................................................................................
  }
} {normal}

#----------------------------------------------------------------------
# Tests exclusive-5.X - test that statement journals are truncated
# instead of deleted when in exclusive access mode.
#
#set sqlite_os_trace 1








do_test exclusive-5.0 {
  execsql {
    CREATE TABLE abc(a UNIQUE, b UNIQUE, c UNIQUE);
    BEGIN;
    INSERT INTO abc VALUES(1, 2, 3);
    INSERT INTO abc SELECT a+1, b+1, c+1 FROM abc;
  }
................................................................................
} {normal 1 2 3 2 3 4 5 6 7 11 12 13 12 13 14 15 16 17}
do_test exclusive-5.7 {
  # Just the db open.
  set sqlite_open_file_count
} {1}

finish_test









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#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library. The focus
# of these tests is exclusive access mode (i.e. the thing activated by 
# "PRAGMA locking_mode = EXCLUSIVE").
#
# $Id: exclusive.test,v 1.4 2007/03/30 16:01:55 drh Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
................................................................................
#----------------------------------------------------------------------
# Test cases exclusive-1.X test the PRAGMA logic.
#
do_test exclusive-1.0 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;
    pragma temp.locking_mode;
  } 
} {normal normal exclusive}
do_test exclusive-1.1 {
  execsql {
    pragma locking_mode = exclusive;
  } 
} {exclusive}
do_test exclusive-1.2 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;
    pragma temp.locking_mode;
  } 
} {exclusive exclusive exclusive}
do_test exclusive-1.3 {
  execsql {
    pragma locking_mode = normal;
  } 
} {normal}
do_test exclusive-1.4 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;
    pragma temp.locking_mode;
  } 
} {normal normal exclusive}
do_test exclusive-1.5 {
  execsql {
    pragma locking_mode = invalid;
  } 
} {normal}
do_test exclusive-1.6 {
  execsql {
    pragma locking_mode;
    pragma main.locking_mode;
    pragma temp.locking_mode;
  } 
} {normal normal exclusive}
do_test exclusive-1.7 {
  execsql {
    pragma locking_mode = exclusive;
    ATTACH 'test2.db' as aux;
  }
  execsql {
    pragma main.locking_mode;
................................................................................
} {exclusive exclusive}
do_test exclusive-1.8 {
  execsql {
    pragma main.locking_mode = normal;
  }
  execsql {
    pragma main.locking_mode;
    pragma temp.locking_mode;
    pragma aux.locking_mode;
  }
} {normal exclusive exclusive}
do_test exclusive-1.9 {
  execsql {
    pragma locking_mode;
  }
} {exclusive}
do_test exclusive-1.10 {
  execsql {
................................................................................
} {normal normal exclusive}
do_test exclusive-1.12 {
  execsql {
    pragma locking_mode = normal;
  }
  execsql {
    pragma main.locking_mode;
    pragma temp.locking_mode;
    pragma aux.locking_mode;
    pragma aux2.locking_mode;
  }
} {normal exclusive normal normal}
do_test exclusive-1.13 {
  execsql {
    ATTACH 'test4.db' as aux3;
  }
  execsql {
    pragma main.locking_mode;
    pragma temp.locking_mode;
    pragma aux.locking_mode;
    pragma aux2.locking_mode;
    pragma aux3.locking_mode;
  }
} {normal exclusive normal normal normal}

do_test exclusive-1.99 {
  execsql {
    DETACH aux;
    DETACH aux2;
    DETACH aux3;
  }
................................................................................
  }
} {normal}

#----------------------------------------------------------------------
# Tests exclusive-5.X - test that statement journals are truncated
# instead of deleted when in exclusive access mode.
#


# Close and reopen the database so that the temp database is no
# longer active.
#
db close
sqlite db test.db


do_test exclusive-5.0 {
  execsql {
    CREATE TABLE abc(a UNIQUE, b UNIQUE, c UNIQUE);
    BEGIN;
    INSERT INTO abc VALUES(1, 2, 3);
    INSERT INTO abc SELECT a+1, b+1, c+1 FROM abc;
  }
................................................................................
} {normal 1 2 3 2 3 4 5 6 7 11 12 13 12 13 14 15 16 17}
do_test exclusive-5.7 {
  # Just the db open.
  set sqlite_open_file_count
} {1}

finish_test

Changes to test/exclusive3.test. 

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# 2001 September 15
#
# 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.
#
#***********************************************************************
#
# This file runs the tests in the file ioerr.test with auto-vacuum enabled
# databases.
#
# $Id: exclusive3.test,v 1.2 2007/03/27 16:19:52 danielk1977 Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
................................................................................
rename sqlite3 ""
rename real_sqlite3 sqlite3
rename finish_test ""
rename really_finish_test2 finish_test
rename do_test ""
rename really_do_test do_test
finish_test


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# 2007 March 26
#
# 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.
#
#***********************************************************************
#
# This file runs the tests in the file ioerr.test with 
# exclusive access mode enabled.
#
# $Id: exclusive3.test,v 1.3 2007/03/30 16:01:55 drh Exp $

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

ifcapable {!pager_pragmas} {
  finish_test
  return
................................................................................
rename sqlite3 ""
rename real_sqlite3 sqlite3
rename finish_test ""
rename really_finish_test2 finish_test
rename do_test ""
rename really_do_test do_test
finish_test

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