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Comment:Ensure that the Pager.changeCountDone flag is cleared whenever dropping the write lock, even when transitioning from EXCLUSIVE locking mode into NORMAL locking mode while in WAL mode. Ticket [fb3b3024ea238d5c].
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SHA3-256: 846b1de6e5a9e418f225273dc033234c64c116fcd89c8261522b4902c248451f
User & Date: drh 2019-12-27 01:50:46
Context
2019-12-27
08:57
When determining if an aggregate within a sub-query should be processed as part of the sub-query or an outer query, consider any FILTER clause in the same way as the arguments to the aggregate. (check-in: 1ffc045d user: dan tags: trunk)
01:50
Ensure that the Pager.changeCountDone flag is cleared whenever dropping the write lock, even when transitioning from EXCLUSIVE locking mode into NORMAL locking mode while in WAL mode. Ticket [fb3b3024ea238d5c]. (check-in: 846b1de6 user: drh tags: trunk)
00:19
Fix buffer underflows in the zipfile extension associated with zero-length or NULL filename in the ZIP archive. But report on the mailing list by Yongheng and Rui. (check-in: 465a15c5 user: drh tags: trunk)
Changes
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Changes to src/pager.c.

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    assert( pPager->eLock>=eLock );
    rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
    if( pPager->eLock!=UNKNOWN_LOCK ){
      pPager->eLock = (u8)eLock;
    }
    IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
  }

  return rc;
}

/*
** Lock the database file to level eLock, which must be either SHARED_LOCK,
** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
** Pager.eLock variable to the new locking state. 
................................................................................
    }

    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
    ** without clearing the error code. This is intentional - the error
    ** code is cleared and the cache reset in the block below.
    */
    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );
    pPager->changeCountDone = 0;
    pPager->eState = PAGER_OPEN;
  }

  /* If Pager.errCode is set, the contents of the pager cache cannot be
  ** trusted. Now that there are no outstanding references to the pager,
  ** it can safely move back to PAGER_OPEN state. This happens in both
  ** normal and exclusive-locking mode.
................................................................................
    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
  }

  if( !pPager->exclusiveMode 
   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
  ){
    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);
    pPager->changeCountDone = 0;
  }
  pPager->eState = PAGER_READER;
  pPager->setMaster = 0;

  return (rc==SQLITE_OK?rc2:rc);
}








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    assert( pPager->eLock>=eLock );
    rc = pPager->noLock ? SQLITE_OK : sqlite3OsUnlock(pPager->fd, eLock);
    if( pPager->eLock!=UNKNOWN_LOCK ){
      pPager->eLock = (u8)eLock;
    }
    IOTRACE(("UNLOCK %p %d\n", pPager, eLock))
  }
  pPager->changeCountDone = pPager->tempFile; /* ticket fb3b3024ea238d5c */
  return rc;
}

/*
** Lock the database file to level eLock, which must be either SHARED_LOCK,
** RESERVED_LOCK or EXCLUSIVE_LOCK. If the caller is successful, set the
** Pager.eLock variable to the new locking state. 
................................................................................
    }

    /* The pager state may be changed from PAGER_ERROR to PAGER_OPEN here
    ** without clearing the error code. This is intentional - the error
    ** code is cleared and the cache reset in the block below.
    */
    assert( pPager->errCode || pPager->eState!=PAGER_ERROR );

    pPager->eState = PAGER_OPEN;
  }

  /* If Pager.errCode is set, the contents of the pager cache cannot be
  ** trusted. Now that there are no outstanding references to the pager,
  ** it can safely move back to PAGER_OPEN state. This happens in both
  ** normal and exclusive-locking mode.
................................................................................
    if( rc==SQLITE_NOTFOUND ) rc = SQLITE_OK;
  }

  if( !pPager->exclusiveMode 
   && (!pagerUseWal(pPager) || sqlite3WalExclusiveMode(pPager->pWal, 0))
  ){
    rc2 = pagerUnlockDb(pPager, SHARED_LOCK);

  }
  pPager->eState = PAGER_READER;
  pPager->setMaster = 0;

  return (rc==SQLITE_OK?rc2:rc);
}

Changes to test/exclusive.test.

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  sqlite3 db test.db
} {}

do_execsql_test exclusive-6.5 {
  PRAGMA locking_mode = EXCLUSIVE;
  SELECT * FROM sqlite_master;
} {exclusive}



















} ;# atomic_batch_write==0

finish_test







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  sqlite3 db test.db
} {}

do_execsql_test exclusive-6.5 {
  PRAGMA locking_mode = EXCLUSIVE;
  SELECT * FROM sqlite_master;
} {exclusive}

# 2019-12-26 ticket fb3b3024ea238d5c
do_test exclusive-7.1 {
  db close
  forcedelete test.db test.db-journal test.db-wal
  sqlite3 db test.db
  # The following sequence of pragmas would trigger an assert()
  # associated with Pager.changeCountDone inside of assert_pager_state(),
  # prior to the fix.
  db eval {
    PRAGMA locking_mode = EXCLUSIVE;
    PRAGMA journal_mode = WAL;
    PRAGMA locking_mode = NORMAL;
    PRAGMA user_version;
    PRAGMA journal_mode = DELETE;
  }
} {exclusive wal normal 0 delete}
 

} ;# atomic_batch_write==0

finish_test