alter.c

sqlite-3.4.1,嵌入式数据库.是一个功能强大的开源数据库,给学习和研发以及小型公司的发展带来了全所未有的好处.

/*
** 2005 February 15
**
** 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 C code routines that used to generate VDBE code
** that implements the ALTER TABLE command.
**
** $Id: alter.c,v 1.27 2007/06/27 17:09:24 danielk1977 Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

/*
** The code in this file only exists if we are not omitting the
** ALTER TABLE logic from the build.
*/
#ifndef SQLITE_OMIT_ALTERTABLE


/*
** This function is used by SQL generated to implement the 
** ALTER TABLE command. The first argument is the text of a CREATE TABLE or
** CREATE INDEX command. The second is a table name. The table name in 
** the CREATE TABLE or CREATE INDEX statement is replaced with the third
** argument and the result returned. Examples:
**
** sqlite_rename_table('CREATE TABLE abc(a, b, c)', 'def')
**     -> 'CREATE TABLE def(a, b, c)'
**
** sqlite_rename_table('CREATE INDEX i ON abc(a)', 'def')
**     -> 'CREATE INDEX i ON def(a, b, c)'
*/
static void renameTableFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  unsigned char const *zSql = sqlite3_value_text(argv[0]);
  unsigned char const *zTableName = sqlite3_value_text(argv[1]);

  int token;
  Token tname;
  unsigned char const *zCsr = zSql;
  int len = 0;
  char *zRet;

  /* The principle used to locate the table name in the CREATE TABLE 
  ** statement is that the table name is the first token that is immediatedly
  ** followed by a left parenthesis - TK_LP - or "USING" TK_USING.
  */
  if( zSql ){
    do {
      if( !*zCsr ){
        /* Ran out of input before finding an opening bracket. Return NULL. */
        return;
      }

      /* Store the token that zCsr points to in tname. */
      tname.z = zCsr;
      tname.n = len;

      /* Advance zCsr to the next token. Store that token type in 'token',
      ** and it's length in 'len' (to be used next iteration of this loop).
      */
      do {
        zCsr += len;
        len = sqlite3GetToken(zCsr, &token);
      } while( token==TK_SPACE );
      assert( len>0 );
    } while( token!=TK_LP && token!=TK_USING );

    zRet = sqlite3MPrintf("%.*s%Q%s", tname.z - zSql, zSql, 
       zTableName, tname.z+tname.n);
    sqlite3_result_text(context, zRet, -1, sqlite3FreeX);
  }
}

#ifndef SQLITE_OMIT_TRIGGER
/* This function is used by SQL generated to implement the
** ALTER TABLE command. The first argument is the text of a CREATE TRIGGER 
** statement. The second is a table name. The table name in the CREATE 
** TRIGGER statement is replaced with the third argument and the result 
** returned. This is analagous to renameTableFunc() above, except for CREATE
** TRIGGER, not CREATE INDEX and CREATE TABLE.
*/
static void renameTriggerFunc(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  unsigned char const *zSql = sqlite3_value_text(argv[0]);
  unsigned char const *zTableName = sqlite3_value_text(argv[1]);

  int token;
  Token tname;
  int dist = 3;
  unsigned char const *zCsr = zSql;
  int len = 0;
  char *zRet;

  /* The principle used to locate the table name in the CREATE TRIGGER 
  ** statement is that the table name is the first token that is immediatedly
  ** preceded by either TK_ON or TK_DOT and immediatedly followed by one
  ** of TK_WHEN, TK_BEGIN or TK_FOR.
  */
  if( zSql ){
    do {

      if( !*zCsr ){
        /* Ran out of input before finding the table name. Return NULL. */
        return;
      }

      /* Store the token that zCsr points to in tname. */
      tname.z = zCsr;
      tname.n = len;

      /* Advance zCsr to the next token. Store that token type in 'token',
      ** and it's length in 'len' (to be used next iteration of this loop).
      */
      do {
        zCsr += len;
        len = sqlite3GetToken(zCsr, &token);
      }while( token==TK_SPACE );
      assert( len>0 );

      /* Variable 'dist' stores the number of tokens read since the most
      ** recent TK_DOT or TK_ON. This means that when a WHEN, FOR or BEGIN 
      ** token is read and 'dist' equals 2, the condition stated above
      ** to be met.
      **
      ** Note that ON cannot be a database, table or column name, so
      ** there is no need to worry about syntax like 
      ** "CREATE TRIGGER ... ON ON.ON BEGIN ..." etc.
      */
      dist++;
      if( token==TK_DOT || token==TK_ON ){
        dist = 0;
      }
    } while( dist!=2 || (token!=TK_WHEN && token!=TK_FOR && token!=TK_BEGIN) );

    /* Variable tname now contains the token that is the old table-name
    ** in the CREATE TRIGGER statement.
    */
    zRet = sqlite3MPrintf("%.*s%Q%s", tname.z - zSql, zSql, 
       zTableName, tname.z+tname.n);
    sqlite3_result_text(context, zRet, -1, sqlite3FreeX);
  }
}
#endif   /* !SQLITE_OMIT_TRIGGER */

/*
** Register built-in functions used to help implement ALTER TABLE
*/
void sqlite3AlterFunctions(sqlite3 *db){
  static const struct {
     char *zName;
     signed char nArg;
     void (*xFunc)(sqlite3_context*,int,sqlite3_value **);
  } aFuncs[] = {
    { "sqlite_rename_table",    2, renameTableFunc},
#ifndef SQLITE_OMIT_TRIGGER
    { "sqlite_rename_trigger",  2, renameTriggerFunc},
#endif
  };
  int i;

  for(i=0; i<sizeof(aFuncs)/sizeof(aFuncs[0]); i++){
    sqlite3CreateFunc(db, aFuncs[i].zName, aFuncs[i].nArg,
        SQLITE_UTF8, 0, aFuncs[i].xFunc, 0, 0);
  }
}

/*
** Generate the text of a WHERE expression which can be used to select all
** temporary triggers on table pTab from the sqlite_temp_master table. If
** table pTab has no temporary triggers, or is itself stored in the 
** temporary database, NULL is returned.
*/
static char *whereTempTriggers(Parse *pParse, Table *pTab){
  Trigger *pTrig;
  char *zWhere = 0;
  char *tmp = 0;
  const Schema *pTempSchema = pParse->db->aDb[1].pSchema; /* Temp db schema */

  /* If the table is not located in the temp-db (in which case NULL is 
  ** returned, loop through the tables list of triggers. For each trigger
  ** that is not part of the temp-db schema, add a clause to the WHERE 
  ** expression being built up in zWhere.
  */
  if( pTab->pSchema!=pTempSchema ){
    for( pTrig=pTab->pTrigger; pTrig; pTrig=pTrig->pNext ){
      if( pTrig->pSchema==pTempSchema ){
        if( !zWhere ){
          zWhere = sqlite3MPrintf("name=%Q", pTrig->name);
        }else{
          tmp = zWhere;
          zWhere = sqlite3MPrintf("%s OR name=%Q", zWhere, pTrig->name);
          sqliteFree(tmp);
        }
      }
    }
  }
  return zWhere;
}

/*
** Generate code to drop and reload the internal representation of table
** pTab from the database, including triggers and temporary triggers.
** Argument zName is the name of the table in the database schema at
** the time the generated code is executed. This can be different from
** pTab->zName if this function is being called to code part of an 
** "ALTER TABLE RENAME TO" statement.
*/
static void reloadTableSchema(Parse *pParse, Table *pTab, const char *zName){
  Vdbe *v;
  char *zWhere;
  int iDb;                   /* Index of database containing pTab */
#ifndef SQLITE_OMIT_TRIGGER
  Trigger *pTrig;
#endif

  v = sqlite3GetVdbe(pParse);
  if( !v ) return;
  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
  assert( iDb>=0 );

#ifndef SQLITE_OMIT_TRIGGER
  /* Drop any table triggers from the internal schema. */
  for(pTrig=pTab->pTrigger; pTrig; pTrig=pTrig->pNext){
    int iTrigDb = sqlite3SchemaToIndex(pParse->db, pTrig->pSchema);
    assert( iTrigDb==iDb || iTrigDb==1 );
    sqlite3VdbeOp3(v, OP_DropTrigger, iTrigDb, 0, pTrig->name, 0);
  }
#endif

  /* Drop the table and index from the internal schema */
  sqlite3VdbeOp3(v, OP_DropTable, iDb, 0, pTab->zName, 0);

  /* Reload the table, index and permanent trigger schemas. */
  zWhere = sqlite3MPrintf("tbl_name=%Q", zName);
  if( !zWhere ) return;
  sqlite3VdbeOp3(v, OP_ParseSchema, iDb, 0, zWhere, P3_DYNAMIC);

#ifndef SQLITE_OMIT_TRIGGER
  /* Now, if the table is not stored in the temp database, reload any temp 
  ** triggers. Don't use IN(...) in case SQLITE_OMIT_SUBQUERY is defined. 
  */
  if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){
    sqlite3VdbeOp3(v, OP_ParseSchema, 1, 0, zWhere, P3_DYNAMIC);
  }
#endif
}

/*
** Generate code to implement the "ALTER TABLE xxx RENAME TO yyy" 
** command. 
*/
void sqlite3AlterRenameTable(
  Parse *pParse,            /* Parser context. */
  SrcList *pSrc,            /* The table to rename. */
  Token *pName              /* The new table name. */
){
  int iDb;                  /* Database that contains the table */
  char *zDb;                /* Name of database iDb */
  Table *pTab;              /* Table being renamed */
  char *zName = 0;          /* NULL-terminated version of pName */ 
  sqlite3 *db = pParse->db; /* Database connection */
  int nTabName;             /* Number of UTF-8 characters in zTabName */
  const char *zTabName;     /* Original name of the table */
  Vdbe *v;
#ifndef SQLITE_OMIT_TRIGGER
  char *zWhere = 0;         /* Where clause to locate temp triggers */
#endif
  int isVirtualRename = 0;  /* True if this is a v-table with an xRename() */
  
  if( sqlite3MallocFailed() ) goto exit_rename_table;
  assert( pSrc->nSrc==1 );

  pTab = sqlite3LocateTable(pParse, pSrc->a[0].zName, pSrc->a[0].zDatabase);
  if( !pTab ) goto exit_rename_table;
  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);
  zDb = db->aDb[iDb].zName;

  /* Get a NULL terminated version of the new table name. */
  zName = sqlite3NameFromToken(pName);
  if( !zName ) goto exit_rename_table;

  /* Check that a table or index named 'zName' does not already exist
  ** in database iDb. If so, this is an error.
  */
  if( sqlite3FindTable(db, zName, zDb) || sqlite3FindIndex(db, zName, zDb) ){
    sqlite3ErrorMsg(pParse, 
        "there is already another table or index with this name: %s", zName);
    goto exit_rename_table;
  }

  /* Make sure it is not a system table being altered, or a reserved name