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Comment:Size and performance optimization for sqlite3Init().
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SHA3-256:776d91284a891bec64d6f649ff17de898b6ac6f66dd3d2afccc394a012a40c7d
User & Date: drh 2017-08-25 15:43:34
Context
2017-08-25
19:51
Fix a few over-length source code lines. No functional changes. check-in: 1783c54c user: drh tags: trunk
15:43
Size and performance optimization for sqlite3Init(). check-in: 776d9128 user: drh tags: trunk
13:34
Small performance optimization in sqlite3WhereBegin(). check-in: 39f708d1 user: drh tags: trunk
Changes
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Changes to src/prepare.c.

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  const char *zMasterName;
  int openedTransaction = 0;

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pSchema );
  assert( sqlite3_mutex_held(db->mutex) );
  assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );



  /* Construct the in-memory representation schema tables (sqlite_master or
  ** sqlite_temp_master) by invoking the parser directly.  The appropriate
  ** table name will be inserted automatically by the parser so we can just
  ** use the abbreviation "x" here.  The parser will also automatically tag
  ** the schema table as read-only. */
  azArg[0] = zMasterName = SCHEMA_TABLE(iDb);
  azArg[1] = "1";
  azArg[2] = "CREATE TABLE x(type text,name text,tbl_name text,"
                            "rootpage integer,sql text)";
  azArg[3] = 0;
  initData.db = db;
  initData.iDb = iDb;
  initData.rc = SQLITE_OK;
  initData.pzErrMsg = pzErrMsg;
  sqlite3InitCallback(&initData, 3, (char **)azArg, 0);
  if( initData.rc ){
................................................................................
    goto error_out;
  }

  /* Create a cursor to hold the database open
  */
  pDb = &db->aDb[iDb];
  if( pDb->pBt==0 ){
    if( !OMIT_TEMPDB && ALWAYS(iDb==1) ){
      DbSetProperty(db, 1, DB_SchemaLoaded);
    }
    return SQLITE_OK;

  }

  /* If there is not already a read-only (or read-write) transaction opened
  ** on the b-tree database, open one now. If a transaction is opened, it 
  ** will be closed before this function returns.  */
  sqlite3BtreeEnter(pDb->pBt);
  if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
................................................................................
initone_error_out:
  if( openedTransaction ){
    sqlite3BtreeCommit(pDb->pBt);
  }
  sqlite3BtreeLeave(pDb->pBt);

error_out:

  if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
    sqlite3OomFault(db);
  }



  return rc;
}

/*
** Initialize all database files - the main database file, the file
** used to store temporary tables, and any additional database files
** created using ATTACH statements.  Return a success code.  If an
................................................................................
int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  int i, rc;
  int commit_internal = !(db->mDbFlags&DBFLAG_SchemaChange);
  
  assert( sqlite3_mutex_held(db->mutex) );
  assert( sqlite3BtreeHoldsMutex(db->aDb[0].pBt) );
  assert( db->init.busy==0 );
  rc = SQLITE_OK;
  db->init.busy = 1;
  ENC(db) = SCHEMA_ENC(db);


  for(i=0; rc==SQLITE_OK && i<db->nDb; i++){
    if( DbHasProperty(db, i, DB_SchemaLoaded) || i==1 ) continue;
    rc = sqlite3InitOne(db, i, pzErrMsg);
    if( rc ){
      sqlite3ResetOneSchema(db, i);
    }
  }

  /* Once all the other databases have been initialized, load the schema
  ** for the TEMP database. This is loaded last, as the TEMP database
  ** schema may contain references to objects in other databases.
  */
#ifndef SQLITE_OMIT_TEMPDB
  assert( db->nDb>1 );


  if( rc==SQLITE_OK && !DbHasProperty(db, 1, DB_SchemaLoaded) ){
    rc = sqlite3InitOne(db, 1, pzErrMsg);
    if( rc ){
      sqlite3ResetOneSchema(db, 1);
    }
  }
#endif

  db->init.busy = 0;
  if( rc==SQLITE_OK && commit_internal ){
    sqlite3CommitInternalChanges(db);
  }

  return rc; 
}

/*
** This routine is a no-op if the database schema is already initialized.
** Otherwise, the schema is loaded. An error code is returned.
*/
int sqlite3ReadSchema(Parse *pParse){







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  const char *zMasterName;
  int openedTransaction = 0;

  assert( iDb>=0 && iDb<db->nDb );
  assert( db->aDb[iDb].pSchema );
  assert( sqlite3_mutex_held(db->mutex) );
  assert( iDb==1 || sqlite3BtreeHoldsMutex(db->aDb[iDb].pBt) );

  db->init.busy = 1;

  /* Construct the in-memory representation schema tables (sqlite_master or
  ** sqlite_temp_master) by invoking the parser directly.  The appropriate
  ** table name will be inserted automatically by the parser so we can just
  ** use the abbreviation "x" here.  The parser will also automatically tag
  ** the schema table as read-only. */
  azArg[0] = zMasterName = SCHEMA_TABLE(iDb);
  azArg[1] = "1";
  azArg[2] = "CREATE TABLE x(type text,name text,tbl_name text,"
                            "rootpage int,sql text)";
  azArg[3] = 0;
  initData.db = db;
  initData.iDb = iDb;
  initData.rc = SQLITE_OK;
  initData.pzErrMsg = pzErrMsg;
  sqlite3InitCallback(&initData, 3, (char **)azArg, 0);
  if( initData.rc ){
................................................................................
    goto error_out;
  }

  /* Create a cursor to hold the database open
  */
  pDb = &db->aDb[iDb];
  if( pDb->pBt==0 ){
    assert( iDb==1 );
    DbSetProperty(db, 1, DB_SchemaLoaded);

    rc = SQLITE_OK;
    goto error_out;
  }

  /* If there is not already a read-only (or read-write) transaction opened
  ** on the b-tree database, open one now. If a transaction is opened, it 
  ** will be closed before this function returns.  */
  sqlite3BtreeEnter(pDb->pBt);
  if( !sqlite3BtreeIsInReadTrans(pDb->pBt) ){
................................................................................
initone_error_out:
  if( openedTransaction ){
    sqlite3BtreeCommit(pDb->pBt);
  }
  sqlite3BtreeLeave(pDb->pBt);

error_out:
  if( rc ){
    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
      sqlite3OomFault(db);
    }
    sqlite3ResetOneSchema(db, iDb);
  }
  db->init.busy = 0;
  return rc;
}

/*
** Initialize all database files - the main database file, the file
** used to store temporary tables, and any additional database files
** created using ATTACH statements.  Return a success code.  If an
................................................................................
int sqlite3Init(sqlite3 *db, char **pzErrMsg){
  int i, rc;
  int commit_internal = !(db->mDbFlags&DBFLAG_SchemaChange);
  
  assert( sqlite3_mutex_held(db->mutex) );
  assert( sqlite3BtreeHoldsMutex(db->aDb[0].pBt) );
  assert( db->init.busy==0 );


  ENC(db) = SCHEMA_ENC(db);
  assert( db->nDb>0 );
  /* Do the main schema first */
  if( !DbHasProperty(db, 0, DB_SchemaLoaded) ){

    rc = sqlite3InitOne(db, 0, pzErrMsg);
    if( rc ) return rc;

  }








  /* All other schemas after the main schema. The "temp" schema must be last */
  for(i=db->nDb-1; i>0; i--){
    if( !DbHasProperty(db, i, DB_SchemaLoaded) ){
      rc = sqlite3InitOne(db, i, pzErrMsg);
      if( rc ) return rc;

    }
  }



  if( commit_internal ){
    sqlite3CommitInternalChanges(db);
  }

  return SQLITE_OK;
}

/*
** This routine is a no-op if the database schema is already initialized.
** Otherwise, the schema is loaded. An error code is returned.
*/
int sqlite3ReadSchema(Parse *pParse){