prepare.c

sqlite 嵌入式数据库的源码

/*
** 2005 May 25
**
** 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.
**
*************************************************************************
** This file contains the implementation of the sqlite3_prepare()
** interface, and routines that contribute to loading the database schema
** from disk.
**
** $Id: prepare.c,v 1.1 2005/05/25 04:11:56 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>

/*
** Fill the InitData structure with an error message that indicates
** that the database is corrupt.
*/
static void corruptSchema(InitData *pData, const char *zExtra){
  if( !sqlite3_malloc_failed ){
    sqlite3SetString(pData->pzErrMsg, "malformed database schema",
       zExtra!=0 && zExtra[0]!=0 ? " - " : (char*)0, zExtra, (char*)0);
  }
}

/*
** This is the callback routine for the code that initializes the
** database.  See sqlite3Init() below for additional information.
** This routine is also called from the OP_ParseSchema opcode of the VDBE.
**
** Each callback contains the following information:
**
**     argv[0] = name of thing being created
**     argv[1] = root page number for table or index.  NULL for trigger or view.
**     argv[2] = SQL text for the CREATE statement.
**     argv[3] = "1" for temporary files, "0" for main database, "2" or more
**               for auxiliary database files.
**
*/
int sqlite3InitCallback(void *pInit, int argc, char **argv, char **azColName){
  InitData *pData = (InitData*)pInit;
  sqlite3 *db = pData->db;
  int iDb;

  assert( argc==4 );
  if( argv==0 ) return 0;   /* Might happen if EMPTY_RESULT_CALLBACKS are on */
  if( argv[1]==0 || argv[3]==0 ){
    corruptSchema(pData, 0);
    return 1;
  }
  iDb = atoi(argv[3]);
  assert( iDb>=0 && iDb<db->nDb );
  if( argv[2] && argv[2][0] ){
    /* Call the parser to process a CREATE TABLE, INDEX or VIEW.
    ** But because db->init.busy is set to 1, no VDBE code is generated
    ** or executed.  All the parser does is build the internal data
    ** structures that describe the table, index, or view.
    */
    char *zErr;
    int rc;
    assert( db->init.busy );
    db->init.iDb = iDb;
    db->init.newTnum = atoi(argv[1]);
    rc = sqlite3_exec(db, argv[2], 0, 0, &zErr);
    db->init.iDb = 0;
    if( SQLITE_OK!=rc ){
      corruptSchema(pData, zErr);
      sqlite3_free(zErr);
      return rc;
    }
  }else{
    /* If the SQL column is blank it means this is an index that
    ** was created to be the PRIMARY KEY or to fulfill a UNIQUE
    ** constraint for a CREATE TABLE.  The index should have already
    ** been created when we processed the CREATE TABLE.  All we have
    ** to do here is record the root page number for that index.
    */
    Index *pIndex;
    pIndex = sqlite3FindIndex(db, argv[0], db->aDb[iDb].zName);
    if( pIndex==0 || pIndex->tnum!=0 ){
      /* This can occur if there exists an index on a TEMP table which
      ** has the same name as another index on a permanent index.  Since
      ** the permanent table is hidden by the TEMP table, we can also
      ** safely ignore the index on the permanent table.
      */
      /* Do Nothing */;
    }else{
      pIndex->tnum = atoi(argv[1]);
    }
  }
  return 0;
}

/*
** Attempt to read the database schema and initialize internal
** data structures for a single database file.  The index of the
** database file is given by iDb.  iDb==0 is used for the main
** database.  iDb==1 should never be used.  iDb>=2 is used for
** auxiliary databases.  Return one of the SQLITE_ error codes to
** indicate success or failure.
*/
static int sqlite3InitOne(sqlite3 *db, int iDb, char **pzErrMsg){
  int rc;
  BtCursor *curMain;
  int size;
  Table *pTab;
  char const *azArg[5];
  char zDbNum[30];
  int meta[10];
  InitData initData;
  char const *zMasterSchema;
  char const *zMasterName = SCHEMA_TABLE(iDb);

  /*
  ** The master database table has a structure like this
  */
  static const char master_schema[] = 
     "CREATE TABLE sqlite_master(\n"
     "  type text,\n"
     "  name text,\n"
     "  tbl_name text,\n"
     "  rootpage integer,\n"
     "  sql text\n"
     ")"
  ;
#ifndef SQLITE_OMIT_TEMPDB
  static const char temp_master_schema[] = 
     "CREATE TEMP TABLE sqlite_temp_master(\n"
     "  type text,\n"
     "  name text,\n"
     "  tbl_name text,\n"
     "  rootpage integer,\n"
     "  sql text\n"
     ")"
  ;
#else
  #define temp_master_schema 0
#endif

  assert( iDb>=0 && iDb<db->nDb );

  /* zMasterSchema and zInitScript are set to point at the master schema
  ** and initialisation script appropriate for the database being
  ** initialised. zMasterName is the name of the master table.
  */
  if( !OMIT_TEMPDB && iDb==1 ){
    zMasterSchema = temp_master_schema;
  }else{
    zMasterSchema = master_schema;
  }
  zMasterName = SCHEMA_TABLE(iDb);

  /* Construct the schema tables.  */
  sqlite3SafetyOff(db);
  azArg[0] = zMasterName;
  azArg[1] = "1";
  azArg[2] = zMasterSchema;
  sprintf(zDbNum, "%d", iDb);
  azArg[3] = zDbNum;
  azArg[4] = 0;
  initData.db = db;
  initData.pzErrMsg = pzErrMsg;
  rc = sqlite3InitCallback(&initData, 4, (char **)azArg, 0);
  if( rc!=SQLITE_OK ){
    sqlite3SafetyOn(db);
    return rc;
  }
  pTab = sqlite3FindTable(db, zMasterName, db->aDb[iDb].zName);
  if( pTab ){
    pTab->readOnly = 1;
  }
  sqlite3SafetyOn(db);

  /* Create a cursor to hold the database open
  */
  if( db->aDb[iDb].pBt==0 ){
    if( !OMIT_TEMPDB && iDb==1 ) DbSetProperty(db, 1, DB_SchemaLoaded);
    return SQLITE_OK;
  }
  rc = sqlite3BtreeCursor(db->aDb[iDb].pBt, MASTER_ROOT, 0, 0, 0, &curMain);
  if( rc!=SQLITE_OK && rc!=SQLITE_EMPTY ){
    sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
    return rc;
  }

  /* Get the database meta information.
  **
  ** Meta values are as follows:
  **    meta[0]   Schema cookie.  Changes with each schema change.
  **    meta[1]   File format of schema layer.
  **    meta[2]   Size of the page cache.
  **    meta[3]   Use freelist if 0.  Autovacuum if greater than zero.
  **    meta[4]   Db text encoding. 1:UTF-8 3:UTF-16 LE 4:UTF-16 BE
  **    meta[5]   The user cookie. Used by the application.
  **    meta[6]   
  **    meta[7]
  **    meta[8]
  **    meta[9]
  **
  ** Note: The hash defined SQLITE_UTF* symbols in sqliteInt.h correspond to
  ** the possible values of meta[4].
  */
  if( rc==SQLITE_OK ){
    int i;
    for(i=0; rc==SQLITE_OK && i<sizeof(meta)/sizeof(meta[0]); i++){
      rc = sqlite3BtreeGetMeta(db->aDb[iDb].pBt, i+1, (u32 *)&meta[i]);
    }
    if( rc ){
      sqlite3SetString(pzErrMsg, sqlite3ErrStr(rc), (char*)0);
      sqlite3BtreeCloseCursor(curMain);
      return rc;
    }
  }else{
    memset(meta, 0, sizeof(meta));
  }
  db->aDb[iDb].schema_cookie = meta[0];

  /* If opening a non-empty database, check the text encoding. For the
  ** main database, set sqlite3.enc to the encoding of the main database.
  ** For an attached db, it is an error if the encoding is not the same
  ** as sqlite3.enc.
  */
  if( meta[4] ){  /* text encoding */
    if( iDb==0 ){
      /* If opening the main database, set db->enc. */
      db->enc = (u8)meta[4];
      db->pDfltColl = sqlite3FindCollSeq(db, db->enc, "BINARY", 6, 0);
    }else{
      /* If opening an attached database, the encoding much match db->enc */
      if( meta[4]!=db->enc ){
        sqlite3BtreeCloseCursor(curMain);
        sqlite3SetString(pzErrMsg, "attached databases must use the same"
            " text encoding as main database", (char*)0);
        return SQLITE_ERROR;
      }
    }
  }

  size = meta[2];
  if( size==0 ){ size = MAX_PAGES; }
  db->aDb[iDb].cache_size = size;

  if( iDb==0 ){
    db->file_format = meta[1];
    if( db->file_format==0 ){
      /* This happens if the database was initially empty */
      db->file_format = 1;
    }

    if( db->file_format==2 || db->file_format==3 ){
      /* File format 2 is treated exactly as file format 1. New 
      ** databases are created with file format 1.
      */ 
      db->file_format = 1;
    }
  }

  /*