SQLite

      int i;                    /* Used to iterate through samples */
      tRowcnt sumEq = 0;        /* Sum of the nEq values */
      tRowcnt avgEq = 0;
      tRowcnt nRow;             /* Number of rows in index */
      i64 nSum100 = 0;          /* Number of terms contributing to sumEq */
      i64 nDist100;             /* Number of distinct values in index */

      if( !pIdx->aiRowEst || iCol>=pIdx->nKeyCol || pIdx->aiRowEst[iCol+1]==0 ){
        nRow = pFinal->anLt[iCol];
        nDist100 = (i64)100 * pFinal->anDLt[iCol];
        nSample--;
      }else{
        nRow = pIdx->aiRowEst[0];
        nDist100 = ((i64)100 * pIdx->aiRowEst[0]) / pIdx->aiRowEst[iCol+1];
      }

  szScratch =
       nMaxCells*sizeof(u8*)                       /* apCell */
     + nMaxCells*sizeof(u16)                       /* szCell */
     + pBt->pageSize;                              /* aSpace1 */

  /* EVIDENCE-OF: R-28375-38319 SQLite will never request a scratch buffer
  ** that is more than 6 times the database page size. */
  assert( szScratch<=6*(int)pBt->pageSize );
  apCell = sqlite3ScratchMalloc( szScratch ); 
  if( apCell==0 ){
    rc = SQLITE_NOMEM;
    goto balance_cleanup;
  }
  szCell = (u16*)&apCell[nMaxCells];
  aSpace1 = (u8*)&szCell[nMaxCells];

        assert( pOld->hdrOffset==0 );
        /* The right pointer of the child page pOld becomes the left
        ** pointer of the divider cell */
        memcpy(apCell[nCell], &pOld->aData[8], 4);
      }else{
        assert( leafCorrection==4 );
        if( szCell[nCell]<4 ){
          /* Do not allow any cells smaller than 4 bytes. If a smaller cell
          ** does exist, pad it with 0x00 bytes. */
          assert( szCell[nCell]==3 );
          assert( apCell[nCell]==&pTemp[iSpace1-3] );
          pTemp[iSpace1++] = 0x00;
          szCell[nCell] = 4;
        }
      }
      nCell++;
    }
  }

      /* Cell pCell is destined for new sibling page pNew. Originally, it
      ** was either part of sibling page iOld (possibly an overflow cell), 
      ** or else the divider cell to the left of sibling page iOld. So,
      ** if sibling page iOld had the same page number as pNew, and if
      ** pCell really was a part of sibling page iOld (not a divider or
      ** overflow cell), we can skip updating the pointer map entries.  */
      if( iOld>=nNew
       || pNew->pgno!=aPgno[iOld]
       || pCell<aOld
       || pCell>=&aOld[usableSize]
      ){
        if( !leafCorrection ){
          ptrmapPut(pBt, get4byte(pCell), PTRMAP_BTREE, pNew->pgno, &rc);
        }
        if( szCell[i]>pNew->minLocal ){
          ptrmapPutOvflPtr(pNew, pCell, &rc);
        }
      }

  /* Close all database connections */
  for(j=0; j<db->nDb; j++){
    struct Db *pDb = &db->aDb[j];
    if( pDb->pBt ){
      if( pDb->pSchema ){
        /* Must clear the KeyInfo cache.  See ticket [e4a18565a36884b00edf] */
        sqlite3BtreeEnter(pDb->pBt);
        for(i=sqliteHashFirst(&pDb->pSchema->idxHash); i; i=sqliteHashNext(i)){
          Index *pIdx = sqliteHashData(i);
          sqlite3KeyInfoUnref(pIdx->pKeyInfo);
          pIdx->pKeyInfo = 0;
        }
        sqlite3BtreeLeave(pDb->pBt);
      }
      sqlite3BtreeClose(pDb->pBt);
      pDb->pBt = 0;
      if( j!=1 ){
        pDb->pSchema = 0;
      }
    }

  if( rc!=SQLITE_OK ){
    if( rc==SQLITE_IOERR_NOMEM ){
      rc = SQLITE_NOMEM;
    }
    sqlite3Error(db, rc);
    goto opendb_out;
  }
  sqlite3BtreeEnter(db->aDb[0].pBt);
  db->aDb[0].pSchema = sqlite3SchemaGet(db, db->aDb[0].pBt);
  sqlite3BtreeLeave(db->aDb[0].pBt);
  db->aDb[1].pSchema = sqlite3SchemaGet(db, 0);

  /* The default safety_level for the main database is 'full'; for the temp
  ** database it is 'NONE'. This matches the pager layer defaults.  
  */
  db->aDb[0].zName = "main";
  db->aDb[0].safety_level = 3;

    Tcl_WrongNumArgs(interp, 1, objv, "DB MODE ?NAME?");
    return TCL_ERROR;
  }

  if( objc==4 ){
    zDb = Tcl_GetString(objv[3]);
  }
  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) || (
      TCL_OK!=Tcl_GetIntFromObj(0, objv[2], &eMode)
   && TCL_OK!=Tcl_GetIndexFromObj(interp, objv[2], aMode, "mode", 0, &eMode) 
  )){
    return TCL_ERROR;
  }

  rc = sqlite3_wal_checkpoint_v2(db, zDb, eMode, &nLog, &nCkpt);
  if( rc!=SQLITE_OK && rc!=SQLITE_BUSY ){
    const char *zErrCode = sqlite3ErrName(rc);
    Tcl_AppendResult(interp, zErrCode, " - ", (char *)sqlite3_errmsg(db), 0);
    return TCL_ERROR;
  }

  pRet = Tcl_NewObj();
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(rc==SQLITE_BUSY?1:0));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nLog));
  Tcl_ListObjAppendElement(interp, pRet, Tcl_NewIntObj(nCkpt));

**
**   void *SRVAL(SorterRecord *p) { return (void*)&p[1]; }
*/
#define SRVAL(p) ((void*)((SorterRecord*)(p) + 1))

/* The minimum PMA size is set to this value multiplied by the database
** page size in bytes.  */
#ifndef SQLITE_SORTER_PMASZ
# define SQLITE_SORTER_PMASZ 250
#endif

/* Maximum number of PMAs that a single MergeEngine can merge */
#define SORTER_MAX_MERGE_COUNT 16

static int vdbeIncrSwap(IncrMerger*);
static void vdbeIncrFree(IncrMerger *);

    pSorter->db = db;
    for(i=0; i<pSorter->nTask; i++){
      SortSubtask *pTask = &pSorter->aTask[i];
      pTask->pSorter = pSorter;
    }

    if( !sqlite3TempInMemory(db) ){
      pSorter->mnPmaSize = SQLITE_SORTER_PMASZ * pgsz;
      mxCache = db->aDb[0].pSchema->cache_size;
      if( mxCache<SQLITE_SORTER_PMASZ ) mxCache = SQLITE_SORTER_PMASZ;
      pSorter->mxPmaSize = MIN((i64)mxCache*pgsz, SQLITE_MAX_MXPMASIZE);

      /* EVIDENCE-OF: R-26747-61719 When the application provides any amount of
      ** scratch memory using SQLITE_CONFIG_SCRATCH, SQLite avoids unnecessary
      ** large heap allocations.
      */
      if( sqlite3GlobalConfig.pScratch==0 ){

  Vdbe *v,                        /* Vdbe to add scanstatus entry to */
  SrcList *pSrclist,              /* FROM clause pLvl reads data from */
  WhereLevel *pLvl,               /* Level to add scanstatus() entry for */
  int addrExplain                 /* Address of OP_Explain (or 0) */
){
  const char *zObj = 0;
  WhereLoop *pLoop = pLvl->pWLoop;
  if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)==0  &&  pLoop->u.btree.pIndex!=0 ){
    zObj = pLoop->u.btree.pIndex->zName;
  }else{
    zObj = pSrclist->a[pLvl->iFrom].zName;
  }
  sqlite3VdbeScanStatus(
      v, addrExplain, pLvl->addrBody, pLvl->addrVisit, pLoop->nOut, zObj
  );

# 2014 December 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.
#
#***********************************************************************
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
source $testdir/lock_common.tcl
source $testdir/wal_common.tcl
set testprefix e_walckpt

# The following two commands are used to determine if any of the files
# "test.db", "test.db2" and "test.db3" are modified by a test case.
#
# The [save_db_hashes] command saves a hash of the current contents of
# all three files in global variables. The [compare_db_hashes] compares
# the current contents with the saved hashes and returns a list of the
# files that have changed.
#
proc save_db_hashes {} {
  global H
  foreach f {test.db test.db2 test.db3} {
    set H($f) 0
    catch { set H($f) [md5file $f] }
  }
}
proc compare_db_hashes {} {
  global H
  set ret [list]
  foreach f {test.db test.db2 test.db3} {
    set expect 0
    catch { set expect [md5file $f] }
    if {$H($f) != $expect} { lappend ret $f }
  }
  set ret
}


# The following tests are run 3 times, each using a different method of 
# invoking a checkpoint:
#
#   1) Using sqlite3_wal_checkpoint_v2()
#   2) Using "PRAGMA wal_checkpoint"
#   3) Using sqlite3_wal_checkpoint() in place of checkpoint_v2(PASSIVE)
#
# Cases (2) and (3) are to show that the following statements are 
# correct, respectively:
#
# EVIDENCE-OF: R-36706-10507 The PRAGMA wal_checkpoint command can be
# used to invoke this interface from SQL.
#
# EVIDENCE-OF: R-41613-20553 The sqlite3_wal_checkpoint(D,X) is
# equivalent to
# sqlite3_wal_checkpoint_v2(D,X,SQLITE_CHECKPOINT_PASSIVE,0,0).
# 
foreach {tn script} {
  1 {
    proc checkpoint {db mode args} {
      eval sqlite3_wal_checkpoint_v2 [list $db] [list $mode] $args
    }
  }

  2 {
    proc checkpoint {db mode args} {
      set sql "PRAGMA wal_checkpoint = $mode"
      if {[llength $args] && [lindex $args 0]!=""} {
        set sql "PRAGMA [lindex $args 0].wal_checkpoint = $mode"
      }
      set rc [catch { $db eval $sql } msg]
      if {$rc} {
        regsub {database} $msg {database:} msg
        error "[sqlite3_errcode $db] - $msg"
      }
      set msg
    }
  }

  3 {
    proc checkpoint {db mode args} {
      if {$mode == "passive"} {
        set rc [eval sqlite3_wal_checkpoint [list $db] $args]
        if {$rc != "SQLITE_OK"} {
          error "$rc - [sqlite3_errmsg $db]"
        }
      } else {
        eval sqlite3_wal_checkpoint_v2 [list $db] [list $mode] $args
      }
    }
  }

} {

  eval $script

  reset_db
  forcedelete test.db2 test.db3 test.db4
  execsql {
    ATTACH 'test.db2' AS aux;
    ATTACH 'test.db3' AS aux2;
    ATTACH 'test.db4' AS aux3;
    CREATE TABLE t1(x);
    CREATE TABLE aux.t2(x);
    CREATE TABLE aux2.t3(x);
    CREATE TABLE aux3.t4(x);
    PRAGMA main.journal_mode = WAL;
    PRAGMA aux.journal_mode = WAL;
    PRAGMA aux2.journal_mode = WAL;
    /* Leave aux4 in rollback mode */
  }

  # EVIDENCE-OF: R-49787-09095 The sqlite3_wal_checkpoint_v2(D,X,M,L,C)
  # interface runs a checkpoint operation on database X of database
  # connection D in mode M. Status information is written back into
  # integers pointed to by L and C.
  #
  #     Tests 1, 2 and 3 below verify the "on database X" part of the
  #     above. Other parts of this requirement are tested below.
  #
  # EVIDENCE-OF: R-00653-06026 If parameter zDb is NULL or points to a
  # zero length string, then the specified operation is attempted on all
  # WAL databases attached to database connection db.
  #
  #     Tests 4 and 5 below test this.
  #
  foreach {tn2 zDb dblist} {
    1 main  test.db
    2 aux   test.db2
    3 aux2  test.db3
    4 ""    {test.db test.db2 test.db3}
    5 -     {test.db test.db2 test.db3}
    6 temp  {}
  } {
    do_test $tn.1.$tn2 {
      execsql {
        INSERT INTO t1 VALUES(1);
        INSERT INTO t2 VALUES(2);
        INSERT INTO t3 VALUES(3);
      }
      save_db_hashes

      if {$zDb == "-"} {
        checkpoint db passive
      } else {
        checkpoint db passive $zDb
      }

      compare_db_hashes
    } $dblist
  }

  # EVIDENCE-OF: R-38207-48996 If zDb is not NULL (or a zero length
  # string) and is not the name of any attached database, SQLITE_ERROR is
  # returned to the caller.
  do_test $tn.2.1 {
    list [catch { checkpoint db passive notadb } msg] $msg
  } {1 {SQLITE_ERROR - unknown database: notadb}}

  # EVIDENCE-OF: R-14303-42483 If database zDb is the name of an attached
  # database that is not in WAL mode, SQLITE_OK is returned and both
  # *pnLog and *pnCkpt set to -1.
  #
  if {$tn==3} {
    # With sqlite3_wal_checkpoint() the two output variables cannot be 
    # tested. So just test that no error is returned when attempting to
    # checkpoint a db in rollback mode.
    do_test $tn.2.2.a { checkpoint db passive aux3 } {}
  } else {
    do_test $tn.2.2.b { checkpoint db passive aux3 } {0 -1 -1}
  }

  # EVIDENCE-OF: R-62028-47212 All calls obtain an exclusive "checkpoint"
  # lock on the database file.
  db close
  testvfs tvfs
  tvfs filter xShmLock
  tvfs script filelock
  proc filelock {method file handle details} {
    # Test for an exclusive checkpoint lock. A checkpoint lock locks a
    # single byte starting at offset 1.
    if {$details == "1 1 lock exclusive"} { set ::seen_checkpoint_lock 1 }
  }
  sqlite3 db test.db -vfs tvfs
  do_test $tn.3.1 {
    execsql { INSERT INTO t1 VALUES('xyz') }
    unset -nocomplain ::seen_checkpoint_lock
    checkpoint db passive
    set ::seen_checkpoint_lock
  } {1}
  db close
  tvfs delete
  reset_db


 

  #-----------------------------------------------------------------------
  # EVIDENCE-OF: R-10421-19736 If any other process is running a
  # checkpoint operation at the same time, the lock cannot be obtained and
  # SQLITE_BUSY is returned.
  #
  # EVIDENCE-OF: R-53820-33897 Even if there is a busy-handler configured,
  # it will not be invoked in this case.
  #
  testvfs tvfs
  tvfs filter xWrite
  sqlite3 db test.db -vfs tvfs
  sqlite3 db2 test.db -vfs tvfs

  do_test $tn.3.2.1 {
    db2 eval {
      PRAGMA journal_mode = WAL;
      CREATE TABLE t1(x, y);
      INSERT INTO t1 VALUES(1,2);
      INSERT INTO t1 VALUES(3,4);
      INSERT INTO t1 VALUES(5,6);
    }
    file size test.db-wal
  } [wal_file_size 5 1024]


  # Connection [db] runs a checkpoint. During this checkpoint, each
  # time it calls xWrite() to write a page into the database file, we
  # attempt to start a checkpoint using [db2]. According to the 
  # first requirement being tested, this should return SQLITE_BUSY. According
  # to the second, the busy-handler belonging to [db2] should not be
  # invoked.
  #
  set ::write_count 0
  set ::write_errors [list]
  proc busy_callback {args} {
    lappend ::write_errors "busy handler called!"
  }
  proc write_callback {args} {
    set rc [catch {checkpoint db2 passive} msg]
    if {0==[regexp "database is locked" $msg] && $msg!="1 -1 -1"} {
      lappend ::write_errors "$rc $msg"
    } 
    incr ::write_count
  }
  db2 busy busy_callback
  tvfs script write_callback

  do_test $tn.3.2.2 {
    db eval {SELECT * FROM sqlite_master}
    checkpoint db full
    set ::write_count
  } {2}

  do_test $tn.3.2.3 {
    set ::write_errors
  } {}

  db close
  db2 close
  tvfs delete

  proc busy_handler {mode busy_handler_mode n} {
    incr ::busy_handler_counter
    switch -- $busy_handler_mode {
      1 {
        # Do nothing. Do not block.
        return 1
      }

      2 {
        # Close first the reader, then later the writer.
        if {$n==5}  { catch {db2 eval commit} }
        if {$n==10} { catch {db3 eval commit} }
        return 0
      }

      3 {
        # Close first the writer, then later the reader.
        if {$n==5}  { catch {db2 eval commit} }
        if {$n==10} { catch {db3 eval commit} }
        return 0
      }
    }
  }

  foreach {mode busy_handler_mode} { 
    passive 1
    full    1
    full    2
    full    3
  } {

    set ::sync_counter 0

    proc tvfs_callback {method args} {
      set tail [file tail [lindex $args 0]]
      if {$method == "xSync" && $tail == "test.db"} {
        incr ::sync_counter
      }

      if {$method == "xWrite" && $tail=="test.db"} {
        if {$::write_ok < 0} {
          set ::write_ok [expr ![catch {db5 eval { BEGIN IMMEDIATE }}]]
          catch { db5 eval ROLLBACK }
        }
        if {$::read_ok < 0} {
          set ::read_ok [expr ![catch {db5 eval { SELECT * FROM t1 }}]]
        }
      }
    }

    catch { db close }
    forcedelete test.db
    testvfs tvfs
    sqlite3 db test.db -vfs tvfs
    #tvfs filter xSync
    tvfs script tvfs_callback

    do_execsql_test $tn.4.$mode.0 {
      CREATE TABLE t1(a, b);
      CREATE TABLE t2(a, b);
      PRAGMA journal_mode = wal;
      INSERT INTO t1 VALUES(1, 2);
      INSERT INTO t1 VALUES(3, 4);
      INSERT INTO t1 VALUES(5, 6);
    } {wal}

    # Open a reader on the current database snapshot.
    do_test $tn.4.$mode.1 {
      sqlite3 db2 test.db -vfs tvfs
      execsql {
        BEGIN;
          SELECT * FROM t1 UNION ALL SELECT * FROM t2;
      } db2
    } {1 2 3 4 5 6}

    # Open a writer. Write a transaction. Then begin, but do not commit,
    # a second transaction.
    do_test $tn.4.$mode.2 {
      sqlite3 db3 test.db -vfs tvfs
      execsql {
        INSERT INTO t2 VALUES(7, 8);
        BEGIN;
          INSERT INTO t2 VALUES(9, 10);
          SELECT * FROM t1 UNION ALL SELECT * FROM t2;
      } db3
    } {1 2 3 4 5 6 7 8 9 10}

    sqlite3 db5 test.db -vfs tvfs

    # Register a busy-handler with connection [db].
    #
    db busy [list busy_handler $mode $busy_handler_mode]
    set ::sync_counter 0
    set ::busy_handler_counter 0
    set ::read_ok -1
    set ::write_ok -1
    
    do_test $tn.4.$mode.3 {
      checkpoint db $mode main
      set {} {}
    } {}

    if { $mode=="passive" } {
      # EVIDENCE-OF: R-16333-64433 Checkpoint as many frames as possible
      # without waiting for any database readers or writers to finish, then
      # sync the database file if all frames in the log were checkpointed.
      #
      #   "As many frames as possible" means all but the last two transactions
      #   (the two that write to table t2, of which the scond is unfinished).
      #   So copying the db file only we see the t1 change, but not the t2
      #   modifications.
      #
      #   The busy handler is not invoked (see below) and the db reader and
      #   writer are still active - so the checkpointer did not wait for either
      #   readers or writers. As a result the checkpoint was not finished and
      #   so the db file is not synced.
      #
      # EVIDENCE-OF: R-62920-47450 The busy-handler callback is never invoked
      # in the SQLITE_CHECKPOINT_PASSIVE mode.
      #
      #   It's not. Test case "$tn.4.$mode.6".
      #
      do_test $tn.4.$mode.4 {
        forcecopy test.db abc.db
        sqlite3 db4 abc.db
        db4 eval { SELECT * FROM t1 UNION ALL SELECT * FROM t2 }
      } {1 2 3 4 5 6}
      do_test $tn.4.$mode.5 { set ::sync_counter } 0
      do_test $tn.4.$mode.6 { set ::busy_handler_counter } 0
      db4 close
  
      db2 eval COMMIT
      db3 eval COMMIT
  
      # EVIDENCE-OF: R-65499-53765 On the other hand, passive mode might leave
      # the checkpoint unfinished if there are concurrent readers or writers.
      #
      #   The reader and writer have now dropped their locks. And so a 
      #   checkpoint now is able to checkpoint more frames. Showing that the
      #   attempt above was left "unfinished".
      #
      #   Also, because the checkpoint finishes this time, the db is synced.
      #   Which is part of R-16333-64433 above.
      #
      do_test $tn.4.$mode.7 {
        checkpoint db $mode main
        forcecopy test.db abc.db
        sqlite3 db4 abc.db
        db4 eval { SELECT * FROM t1 UNION ALL SELECT * FROM t2 }
      } {1 2 3 4 5 6 7 8 9 10}
      do_test $tn.4.$mode.6 { set ::sync_counter } 1
      do_test $tn.4.$mode.7 { set ::busy_handler_counter } 0
      db4 close
    }

    if { $mode=="full" } {
      if {$busy_handler_mode==2 || $busy_handler_mode==3} {
        # EVIDENCE-OF: R-59171-47567 This mode blocks (it invokes the
        # busy-handler callback) until there is no database writer and all
        # readers are reading from the most recent database snapshot.
        #
        #   Show that both the reader and writer have finished:
        #
        do_test $tn.4.$mode.7 {
          list [catchsql COMMIT db2] [catchsql COMMIT db3]
        } [list                                             \
            {1 {cannot commit - no transaction is active}}  \
            {1 {cannot commit - no transaction is active}}  \
        ]

        # EVIDENCE-OF: R-29177-48281 It then checkpoints all frames in the log
        # file and syncs the database file.
        #
        do_test $tn.4.$mode.8 {
          forcecopy test.db abc.db
          sqlite3 db4 abc.db
          db4 eval { SELECT * FROM t1 UNION ALL SELECT * FROM t2 }
        } {1 2 3 4 5 6 7 8 9 10}
        do_test $tn.4.$mode.9 { set ::sync_counter } 1
        db4 close

        # EVIDENCE-OF: R-51867-44713 This mode blocks new database writers
        # while it is pending, but new database readers are allowed to continue
        # unimpeded.
        do_test $tn.4.$mode.10 {
          list $::write_ok $::read_ok
        } {0 1}

      }
    }

    db2 close
    db3 close
    db5 close
  }

  db close
  tvfs delete
}

#-----------------------------------------------------------------------
# EVIDENCE-OF: R-03996-12088 The M parameter must be a valid checkpoint
# mode:
#
#   Valid checkpoint modes are 0, 1, 2 and 3.
#
sqlite3 db test.db
foreach {tn mode res} {
  0 -1001    {1 {SQLITE_MISUSE - not an error}}
  1 -1       {1 {SQLITE_MISUSE - not an error}}
  2  0       {0 {0 -1 -1}}
  3  1       {0 {0 -1 -1}}
  4  2       {0 {0 -1 -1}}
  5  3       {0 {0 -1 -1}}
  6  4       {1 {SQLITE_MISUSE - not an error}}
  7  114     {1 {SQLITE_MISUSE - not an error}}
  8  1000000 {1 {SQLITE_MISUSE - not an error}}
} {
  do_test 4.$tn {
    list [catch "sqlite3_wal_checkpoint_v2 db $mode" msg] $msg
  } $res
}


finish_test

  launch_thread(&err, &threads, dynamic_triggers_2, 0);
  launch_thread(&err, &threads, dynamic_triggers_1, 0);

  join_all_threads(&err, &threads);

  print_and_free_err(&err);
}



#include "tt3_checkpoint.c"
#include "tt3_index.c"

int main(int argc, char **argv){
  struct ThreadTest {
    void (*xTest)(int);
    const char *zTest;
    int nMs;
  } aTest[] = {
    { walthread1, "walthread1", 20000 },
    { walthread2, "walthread2", 20000 },
    { walthread3, "walthread3", 20000 },
    { walthread4, "walthread4", 20000 },
    { walthread5, "walthread5",  1000 },
    { walthread5, "walthread5",  1000 },
    
    { cgt_pager_1,      "cgt_pager_1", 0 },
    { dynamic_triggers, "dynamic_triggers", 20000 },

    { checkpoint_starvation_1, "checkpoint_starvation_1", 10000 },
    { checkpoint_starvation_2, "checkpoint_starvation_2", 10000 },

    { create_drop_index_1, "create_drop_index_1", 10000 },
  };

  int i;
  char *zTest = 0;
  int nTest = 0;
  int bTestfound = 0;
  int bPrefix = 0;

/*
** 2014 December 9
**
** 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.
**
*************************************************************************
**
**     create_drop_index_1
*/


static char *create_drop_index_thread(int iTid, int iArg){
  Error err = {0};                /* Error code and message */
  Sqlite db = {0};                /* SQLite database connection */

  while( !timetostop(&err) ){
    opendb(&err, &db, "test.db", 0);

    sql_script(&err, &db, 

      "DROP INDEX IF EXISTS i1;"
      "DROP INDEX IF EXISTS i2;"
      "DROP INDEX IF EXISTS i3;"
      "DROP INDEX IF EXISTS i4;"

      "CREATE INDEX IF NOT EXISTS i1 ON t1(a);"
      "CREATE INDEX IF NOT EXISTS i2 ON t1(b);"
      "CREATE INDEX IF NOT EXISTS i3 ON t1(c);"
      "CREATE INDEX IF NOT EXISTS i4 ON t1(d);"

      "SELECT * FROM t1 ORDER BY a;"
      "SELECT * FROM t1 ORDER BY b;"
      "SELECT * FROM t1 ORDER BY c;"
      "SELECT * FROM t1 ORDER BY d;"
    );

    closedb(&err, &db);
  }

  print_and_free_err(&err);
  return sqlite3_mprintf("ok");
}

static void create_drop_index_1(int nMs){
  Error err = {0};
  Sqlite db = {0};
  Threadset threads = {0};

  opendb(&err, &db, "test.db", 1);
  sql_script(&err, &db, 
     "CREATE TABLE t1(a, b, c, d);"
     "WITH data(x) AS (SELECT 1 UNION ALL SELECT x+1 FROM data WHERE x<100) "
     "INSERT INTO t1 SELECT x,x,x,x FROM data;"
  );
  closedb(&err, &db);

  setstoptime(&err, nMs);

  sqlite3_enable_shared_cache(1);
  launch_thread(&err, &threads, create_drop_index_thread, 0);
  launch_thread(&err, &threads, create_drop_index_thread, 0);
  launch_thread(&err, &threads, create_drop_index_thread, 0);
  launch_thread(&err, &threads, create_drop_index_thread, 0);
  launch_thread(&err, &threads, create_drop_index_thread, 0);
  sqlite3_enable_shared_cache(0);

  join_all_threads(&err, &threads);
  print_and_free_err(&err);
}