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Overview
Comment:Avoid unnecessary calls to sqlite3BtreeEnterAll() and sqlite3BtreeLeaveAll() when no btree is using shared-cache.
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SHA1: cfb3158204628eb2fd170090a7f212df0e4ce6c9
User & Date: drh 2017-01-02 18:19:29.939
Context
2017-01-02
18:40
Change SQLITE_DEFAULT_PCACHE_INITSZ from 100 to 20, which is experimentally determined to be slightly faster. (check-in: 12d9493cb2 user: drh tags: trunk)
18:19
Avoid unnecessary calls to sqlite3BtreeEnterAll() and sqlite3BtreeLeaveAll() when no btree is using shared-cache. (check-in: cfb3158204 user: drh tags: trunk)
12:20
Add the --all option to the wordcount test program. Fix the speedtest1 test program so that it builds on MSVC and so that the --lookaside 0 0 option works. (check-in: cb338f367e user: drh tags: trunk)
Changes
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Changes to src/attach.c.
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    return;
  }
  assert( pVfs );
  flags |= SQLITE_OPEN_MAIN_DB;
  rc = sqlite3BtreeOpen(pVfs, zPath, db, &aNew->pBt, 0, flags);
  sqlite3_free( zPath );
  db->nDb++;
  db->skipBtreeMutex = 0;
  if( rc==SQLITE_CONSTRAINT ){
    rc = SQLITE_ERROR;
    zErrDyn = sqlite3MPrintf(db, "database is already attached");
  }else if( rc==SQLITE_OK ){
    Pager *pPager;
    aNew->pSchema = sqlite3SchemaGet(db, aNew->pBt);
    if( !aNew->pSchema ){
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Changes to src/btmutex.c.
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** There is a corresponding leave-all procedures.
**
** Enter the mutexes in accending order by BtShared pointer address
** to avoid the possibility of deadlock when two threads with
** two or more btrees in common both try to lock all their btrees
** at the same instant.
*/
void sqlite3BtreeEnterAll(sqlite3 *db){
static void SQLITE_NOINLINE btreeEnterAll(sqlite3 *db){
  int i;
  int skipOk = 1;
  Btree *p;
  assert( sqlite3_mutex_held(db->mutex) );
  for(i=0; i<db->nDb; i++){
    p = db->aDb[i].pBt;
    if( p && p->sharable ){
    if( p ) sqlite3BtreeEnter(p);
      sqlite3BtreeEnter(p);
      skipOk = 0;
  }
}
  db->skipBtreeMutex = skipOk;
}
void sqlite3BtreeEnterAll(sqlite3 *db){
  if( db->skipBtreeMutex==0 ) btreeEnterAll(db);
}
void sqlite3BtreeLeaveAll(sqlite3 *db){
static void SQLITE_NOINLINE btreeLeaveAll(sqlite3 *db){
  int i;
  Btree *p;
  assert( sqlite3_mutex_held(db->mutex) );
  for(i=0; i<db->nDb; i++){
    p = db->aDb[i].pBt;
    if( p ) sqlite3BtreeLeave(p);
  }
}
void sqlite3BtreeLeaveAll(sqlite3 *db){
  if( db->skipBtreeMutex==0 ) btreeLeaveAll(db);
}

#ifndef NDEBUG
/*
** Return true if the current thread holds the database connection
** mutex and all required BtShared mutexes.
**
** This routine is used inside assert() statements only.
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Changes to src/sqliteInt.h.
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  u8 bBenignMalloc;             /* Do not require OOMs if true */
  u8 dfltLockMode;              /* Default locking-mode for attached dbs */
  signed char nextAutovac;      /* Autovac setting after VACUUM if >=0 */
  u8 suppressErr;               /* Do not issue error messages if true */
  u8 vtabOnConflict;            /* Value to return for s3_vtab_on_conflict() */
  u8 isTransactionSavepoint;    /* True if the outermost savepoint is a TS */
  u8 mTrace;                    /* zero or more SQLITE_TRACE flags */
  u8 skipBtreeMutex;            /* True if no shared-cache backends */
  int nextPagesize;             /* Pagesize after VACUUM if >0 */
  u32 magic;                    /* Magic number for detect library misuse */
  int nChange;                  /* Value returned by sqlite3_changes() */
  int nTotalChange;             /* Value returned by sqlite3_total_changes() */
  int aLimit[SQLITE_N_LIMIT];   /* Limits */
  int nMaxSorterMmap;           /* Maximum size of regions mapped by sorter */
  struct sqlite3InitInfo {      /* Information used during initialization */
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