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Overview
Comment:Omit the check for conflicting shared-cache locks in sqlite3Prepare() if the database connection uses no shared cache. We might be able to go back and remove this code completely, due to the newer Schema.iGeneration logic, but that will take more analysis. This check-in gives the speed benefit but not the reduction in code size.
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SHA3-256: 0b73a09270dfafb27f8d1762b547ef8178c9da66f45e7153ff0b76272dfa92f5
User & Date: drh 2019-10-05 19:53:21
Context
2019-10-07
01:05
Fix the OP_SeekRowid opcode so that it works correctly with a Real argument without damaging the value in the register that is the argument. Ticket [b2d4edaffdc156cc]. Test cases in TH3. check-in: 3cde82c8 user: drh tags: trunk
2019-10-05
19:53
Omit the check for conflicting shared-cache locks in sqlite3Prepare() if the database connection uses no shared cache. We might be able to go back and remove this code completely, due to the newer Schema.iGeneration logic, but that will take more analysis. This check-in gives the speed benefit but not the reduction in code size. check-in: 0b73a092 user: drh tags: trunk
19:24
Optimization to sqlite3VtabUnlockList() for the common case when there is no work to do. check-in: fc8d4508 user: drh tags: trunk
Changes
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Changes to src/prepare.c.

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  ** locks on the schema, we just need to make sure nobody else is 
  ** holding them.
  **
  ** Note that setting READ_UNCOMMITTED overrides most lock detection,
  ** but it does *not* override schema lock detection, so this all still
  ** works even if READ_UNCOMMITTED is set.
  */

  for(i=0; i<db->nDb; i++) {
    Btree *pBt = db->aDb[i].pBt;
    if( pBt ){
      assert( sqlite3BtreeHoldsMutex(pBt) );
      rc = sqlite3BtreeSchemaLocked(pBt);
      if( rc ){
        const char *zDb = db->aDb[i].zDbSName;
        sqlite3ErrorWithMsg(db, rc, "database schema is locked: %s", zDb);
        testcase( db->flags & SQLITE_ReadUncommit );
        goto end_prepare;

      }
    }
  }

  sqlite3VtabUnlockList(db);

  sParse.db = db;







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  ** locks on the schema, we just need to make sure nobody else is 
  ** holding them.
  **
  ** Note that setting READ_UNCOMMITTED overrides most lock detection,
  ** but it does *not* override schema lock detection, so this all still
  ** works even if READ_UNCOMMITTED is set.
  */
  if( !db->noSharedCache ){
    for(i=0; i<db->nDb; i++) {
      Btree *pBt = db->aDb[i].pBt;
      if( pBt ){
        assert( sqlite3BtreeHoldsMutex(pBt) );
        rc = sqlite3BtreeSchemaLocked(pBt);
        if( rc ){
          const char *zDb = db->aDb[i].zDbSName;
          sqlite3ErrorWithMsg(db, rc, "database schema is locked: %s", zDb);
          testcase( db->flags & SQLITE_ReadUncommit );
          goto end_prepare;
        }
      }
    }
  }

  sqlite3VtabUnlockList(db);

  sParse.db = db;