testcase( mxFrame==HASHTABLE_NPAGE_ONE-1 );
  testcase( mxFrame==HASHTABLE_NPAGE_ONE );
  testcase( mxFrame==HASHTABLE_NPAGE_ONE+1 );

  if( mxFrame==0 ) return;

  /* Obtain pointers to the hash-table and page-number array containing 
  ** the entry that corresponds to frame pWal->hdr.mxFrame. It is guaranteed
  ** that the page said hash-table and array reside on is already mapped.
  */
  assert( pWal->nWiData>walFramePage(iExternal) );
  assert( pWal->apWiData[walFramePage(iExternal)] );
  walHashGet(pWal, walFramePage(iExternal), &sLoc);

  /* Zero all hash-table entries that correspond to frame numbers greater
  ** than pWal->hdr.mxFrame.
  */
................................................................................
      ** occurs if some other writer has crashed while committing a 
      ** transaction to this database since the current concurrent transaction
      ** was opened.  */
      rc = SQLITE_BUSY_SNAPSHOT;
    }else if( memcmp(&pWal->hdr, (void*)&head, sizeof(WalIndexHdr))!=0 ){
      int bWal2 = isWalMode2(pWal);
      int iHash;
      int iLastHash = walFramePage(head.mxFrame);
      int nLoop = 1+(bWal2 && walidxGetFile(&head)!=walidxGetFile(&pWal->hdr));
      int iLoop;
      

      assert( nLoop==1 || nLoop==2 );
      for(iLoop=0; iLoop<nLoop && rc==SQLITE_OK; iLoop++){
        u32 iFirst;               /* First (external) wal frame to check */
        u32 iLastHash;            /* Last hash to check this loop */
        u32 mxFrame;              /* Last (external) wal frame to check */

        if( bWal2==0 ){
          assert( iLoop==0 );
          /* Special case for wal mode. If this concurrent transaction was
................................................................................
              if( sLoc.aPgno[i]==1 ){
                /* Check that the schema cookie has not been modified. If
                ** it has not, the commit can proceed. */
                u8 aNew[4];
                u8 *aOld = &((u8*)pPage1->pData)[40];
                int sz;
                i64 iOff;
                int iFrame = sLoc.iZero + i;
                int iWal = 0;
                if( bWal2 ){
                  iWal = walExternalDecode(iFrame, &iFrame);
                }
                sz = pWal->hdr.szPage;
                sz = (sz&0xfe00) + ((sz&0x0001)<<16);
                iOff = walFrameOffset(iFrame, sz) + WAL_FRAME_HDRSIZE + 40;
................................................................................

    assert( isWalMode2(pWal) || iWal==0 );

    /* Restore the clients cache of the wal-index header to the state it
    ** was in before the client began writing to the database. 
    */
    memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));

















    assert( walidxGetFile(&pWal->hdr)==iWal );




    iNew = walidxGetMxFrame(&pWal->hdr, walidxGetFile(&pWal->hdr));

    for(iFrame=iNew+1; ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; iFrame++){
      /* This call cannot fail. Unless the page for which the page number
      ** is passed as the second argument is (a) in the cache and 
      ** (b) has an outstanding reference, then xUndo is either a no-op
      ** (if (a) is false) or simply expels the page from the cache (if (b)
      ** is false).

  testcase( mxFrame==HASHTABLE_NPAGE_ONE-1 );
  testcase( mxFrame==HASHTABLE_NPAGE_ONE );
  testcase( mxFrame==HASHTABLE_NPAGE_ONE+1 );

  if( mxFrame==0 ) return;

  /* Obtain pointers to the hash-table and page-number array containing 
  ** the entry that corresponds to frame pWal->hdr.mxFrame.  */


  assert( pWal->nWiData>walFramePage(iExternal) );
  assert( pWal->apWiData[walFramePage(iExternal)] );
  walHashGet(pWal, walFramePage(iExternal), &sLoc);

  /* Zero all hash-table entries that correspond to frame numbers greater
  ** than pWal->hdr.mxFrame.
  */
................................................................................
      ** occurs if some other writer has crashed while committing a 
      ** transaction to this database since the current concurrent transaction
      ** was opened.  */
      rc = SQLITE_BUSY_SNAPSHOT;
    }else if( memcmp(&pWal->hdr, (void*)&head, sizeof(WalIndexHdr))!=0 ){
      int bWal2 = isWalMode2(pWal);
      int iHash;

      int nLoop = 1+(bWal2 && walidxGetFile(&head)!=walidxGetFile(&pWal->hdr));
      int iLoop;
      

      assert( nLoop==1 || nLoop==2 );
      for(iLoop=0; rc==SQLITE_OK && iLoop<nLoop; iLoop++){
        u32 iFirst;               /* First (external) wal frame to check */
        u32 iLastHash;            /* Last hash to check this loop */
        u32 mxFrame;              /* Last (external) wal frame to check */

        if( bWal2==0 ){
          assert( iLoop==0 );
          /* Special case for wal mode. If this concurrent transaction was
................................................................................
              if( sLoc.aPgno[i]==1 ){
                /* Check that the schema cookie has not been modified. If
                ** it has not, the commit can proceed. */
                u8 aNew[4];
                u8 *aOld = &((u8*)pPage1->pData)[40];
                int sz;
                i64 iOff;
                u32 iFrame = sLoc.iZero + i;
                int iWal = 0;
                if( bWal2 ){
                  iWal = walExternalDecode(iFrame, &iFrame);
                }
                sz = pWal->hdr.szPage;
                sz = (sz&0xfe00) + ((sz&0x0001)<<16);
                iOff = walFrameOffset(iFrame, sz) + WAL_FRAME_HDRSIZE + 40;
................................................................................

    assert( isWalMode2(pWal) || iWal==0 );

    /* Restore the clients cache of the wal-index header to the state it
    ** was in before the client began writing to the database. 
    */
    memcpy(&pWal->hdr, (void *)walIndexHdr(pWal), sizeof(WalIndexHdr));
    iNew = walidxGetMxFrame(&pWal->hdr, walidxGetFile(&pWal->hdr));

    /* BEGIN CONCURRENT transactions are different, as the header just
    ** memcpy()d into pWal->hdr may not be the same as the current header 
    ** when the transaction was started. Instead, pWal->hdr now contains
    ** the header written by the most recent successful COMMIT. Because
    ** Wal.writeLock is set, if this is a BEGIN CONCURRENT transaction,
    ** the rollback must be taking place because an error occurred during
    ** a COMMIT.
    **
    ** The code below is still valid. All frames between (iNew+1) and iMax 
    ** must have been written by this transaction before the error occurred.
    ** The exception is in wal2 mode - if the current wal file at the time
    ** of the last COMMIT is not wal file iWal, then the error must have
    ** occurred in WalLockForCommit(), before any pages were written
    ** to the database file. In this case return early.  */
#ifndef SQLITE_OMIT_CONCURRENT
    if( walidxGetFile(&pWal->hdr)!=iWal ){
      assert( isWalMode2(pWal) );
      return SQLITE_OK;
    }
#endif
    assert( walidxGetFile(&pWal->hdr)==iWal );

    for(iFrame=iNew+1; ALWAYS(rc==SQLITE_OK) && iFrame<=iMax; iFrame++){
      /* This call cannot fail. Unless the page for which the page number
      ** is passed as the second argument is (a) in the cache and 
      ** (b) has an outstanding reference, then xUndo is either a no-op
      ** (if (a) is false) or simply expels the page from the cache (if (b)
      ** is false).

# 2018 Dec 28
#
# 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 contains fault injection tests designed to test the concurrent
# transactions feature.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
source $testdir/malloc_common.tcl
set testprefix concfault2

ifcapable !concurrent {
  finish_test
  return
}

do_execsql_test 1.0 {
  PRAGMA auto_vacuum = 0;
  PRAGMA journal_mode = wal2;
  CREATE TABLE t1(a PRIMARY KEY, b);
  CREATE TABLE t2(a PRIMARY KEY, b);
  INSERT INTO t1 VALUES(randomblob(1000), randomblob(100));
  INSERT INTO t1 SELECT randomblob(1000), randomblob(1000) FROM t1;
  INSERT INTO t1 SELECT randomblob(1000), randomblob(1000) FROM t1;
  INSERT INTO t1 SELECT randomblob(1000), randomblob(1000) FROM t1;
  INSERT INTO t1 SELECT randomblob(1000), randomblob(1000) FROM t1;
  DELETE FROM t1 WHERE rowid%2;
} {wal2}

do_test 1.1 {
  list [expr [file size test.db-wal]>75000] [file size test.db-shm]
} {1 32768}

faultsim_save_and_close

do_faultsim_test 1 -prep {
  faultsim_restore_and_reopen
  execsql {
    BEGIN CONCURRENT;
      INSERT INTO t2 VALUES(1, 2);
  }
  sqlite3 db2 test.db
  execsql {
    PRAGMA journal_size_limit = 10000;
    INSERT INTO t1 VALUES(randomblob(1000), randomblob(1000));
  } db2
  db2 close
} -body {
  execsql { COMMIT }
} -test {
  faultsim_test_result {0 {}} 
  catchsql { ROLLBACK }
  faultsim_integrity_check
}
finish_test

source $testdir/wal_common.tcl
set ::testprefix concurrent2

ifcapable !concurrent {
  finish_test
  return
}





do_multiclient_test tn {

  do_test 1.$tn.1 {
    sql1 {
      PRAGMA journal_mode = wal;
      CREATE TABLE t1(x);

source $testdir/wal_common.tcl
set ::testprefix concurrent2

ifcapable !concurrent {
  finish_test
  return
}

do_test 0.1 {
  llength [sqlite3_wal_info db main]
} {2}

do_multiclient_test tn {

  do_test 1.$tn.1 {
    sql1 {
      PRAGMA journal_mode = wal;
      CREATE TABLE t1(x);

walshared.test walslow.test wal.test
wal2savepoint.test wal2lock.test wal2recover2.test

  wal2concurrent.test
  concurrent.test concurrent2.test concurrent3.test
  concurrent4.test concurrent5.test concurrent6.test
  concurrent7.test


  walvfs.test walfault2.test nockpt.test
  snapshot2.test snapshot3.test snapshot4.test
  snapshot_fault.test snapshot.test snapshot_up.test
  walcrash2.test walcrash3.test walcrash4.test walcrash.test
  wal2fault.test
} 

walshared.test walslow.test wal.test
wal2savepoint.test wal2lock.test wal2recover2.test

  wal2concurrent.test
  concurrent.test concurrent2.test concurrent3.test
  concurrent4.test concurrent5.test concurrent6.test
  concurrent7.test
  concfault.test concfault2.test

  walvfs.test walfault2.test nockpt.test
  snapshot2.test snapshot3.test snapshot4.test
  snapshot_fault.test snapshot.test snapshot_up.test
  walcrash2.test walcrash3.test walcrash4.test walcrash.test
  wal2fault.test
} 

      SELECT sum(x) FROM t1;
      SELECT sum(x) FROM t2;
    } db2
  } $res
  db2 close
}












































#-------------------------------------------------------------------------
reset_db
do_execsql_test 1.0 {
  CREATE TABLE t1(a, b, c);
  CREATE INDEX t1a ON t1(a);
  CREATE INDEX t1b ON t1(b);
  CREATE INDEX t1c ON t1(c);

      SELECT sum(x) FROM t1;
      SELECT sum(x) FROM t2;
    } db2
  } $res
  db2 close
}


#-------------------------------------------------------------------------
reset_db
do_execsql_test 1.8.1 {
  PRAGMA autovacuum = 0;
  PRAGMA page_size = 4096;
  CREATE TABLE t1(x);
  CREATE TABLE t2(x);
  WITH s(i) AS ( VALUES(1) UNION ALL SELECT i+1 FROM s WHERE i<1500 )
    INSERT INTO t1 SELECT i FROM s;
  WITH s(i) AS ( VALUES(1) UNION ALL SELECT i+1 FROM s WHERE i<1500 )
    INSERT INTO t2 SELECT i FROM s;

  PRAGMA journal_mode = wal2;
  PRAGMA journal_size_limit = 10000;

  WITH s(i) AS ( VALUES(1) UNION ALL SELECT i+1 FROM s WHERE i<1500 )
    INSERT INTO t2 SELECT i FROM s;
} {wal2 10000}

do_test 1.8.2 {
  list [file size test.db-wal] [file size test.db-wal2]
} {24752 0}

do_execsql_test 1.8.3 { PRAGMA user_version = 123 }
do_test 1.8.4 {
  list [file size test.db-wal] [file size test.db-wal2]
} {24752 4152}

do_test 1.8.5 {
  hexio_write test.db-wal2 [expr 56+16] 0400
  fix_wal_cksums test.db-wal2
} {}

do_test 1.8.6 {
  forcecopy test.db test.db2
  forcecopy test.db-wal test.db2-wal
  forcecopy test.db-wal2 test.db2-wal2
  sqlite3 db2 test.db2
  catchsql { SELECT * FROM sqlite_master } db2
} {1 {database disk image is malformed}}
db2 close

#-------------------------------------------------------------------------
reset_db
do_execsql_test 1.0 {
  CREATE TABLE t1(a, b, c);
  CREATE INDEX t1a ON t1(a);
  CREATE INDEX t1b ON t1(b);
  CREATE INDEX t1c ON t1(c);

    ROLLBACK TO abc;
    WITH s(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM s where i < 10)
    INSERT INTO t1 SELECT random(), random(), random() FROM s;
  COMMIT;
  SELECT count(*) FROM t1;
  PRAGMA integrity_check;
} {210 ok}















finish_test

    ROLLBACK TO abc;
    WITH s(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM s where i < 10)
    INSERT INTO t1 SELECT random(), random(), random() FROM s;
  COMMIT;
  SELECT count(*) FROM t1;
  PRAGMA integrity_check;
} {210 ok}

do_execsql_test 1.4 {
  BEGIN;
    SAVEPOINT abc;
      WITH s(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM s where i < 100)
      INSERT INTO t1 SELECT random(), random(), random() FROM s;
    ROLLBACK TO abc;
    WITH s(i) AS ( SELECT 1 UNION ALL SELECT i+1 FROM s where i < 10)
    INSERT INTO t1 SELECT random(), random(), random() FROM s;
  COMMIT;
  SELECT count(*) FROM t1;
  PRAGMA integrity_check;
} {220 ok}


finish_test

    do_test 1.6 {
      execsql BEGIN
      set SNAPSHOT [sqlite3_snapshot_get_blob db main]
      sqlite3_snapshot_open_blob db main $SNAPSHOT
      execsql COMMIT
    } {}
  } else {

    do_test 2.6 {
      execsql BEGIN









      set res [
        list [catch { sqlite3_snapshot_open_blob db main $SNAPSHOT } msg] $msg
      ]
      execsql COMMIT
      set res
    } {1 SQLITE_ERROR}
  }
}


finish_test

    do_test 1.6 {
      execsql BEGIN
      set SNAPSHOT [sqlite3_snapshot_get_blob db main]
      sqlite3_snapshot_open_blob db main $SNAPSHOT
      execsql COMMIT
    } {}
  } else {

    do_test 2.6.1 {
      execsql BEGIN
      set res [
        list [catch { sqlite3_snapshot_open_blob db main $SNAPSHOT } msg] $msg
      ]
      execsql COMMIT
      set res
    } {1 SQLITE_ERROR}
    do_test 2.6.2 {
      execsql BEGIN
      execsql {SELECT * FROM sqlite_master}
      set res [
        list [catch { sqlite3_snapshot_open_blob db main $SNAPSHOT } msg] $msg
      ]
      execsql COMMIT
      set res
    } {1 SQLITE_ERROR}
  }
}


finish_test