/*

** 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 1.48 2008/08/08 14:19:41 drh 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;

  sqlite3 *db = sqlite3_context_db_handle(context);

  /* The principle used to locate the table name in the CREATE TABLE 

  ** statement is that the table name is the first non-space token that

  ** is immediately followed by a TK_LP or TK_USING token.

  */

  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 its 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(db, "%.*s\"%w\"%s", tname.z - zSql, zSql, 

       zTableName, tname.z+tname.n);

    sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);

  }

}

#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;

  sqlite3 *db = sqlite3_context_db_handle(context);

  /* 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 its 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(db, "%.*s\"%w\"%s", tname.z - zSql, zSql, 

       zTableName, tname.z+tname.n);

    sqlite3_result_text(context, zRet, -1, SQLITE_DYNAMIC);

  }

}

#endif   /* !SQLITE_OMIT_TRIGGER */

/*

** Register built-in functions used to help implement ALTER TABLE

*/

void sqlite3AlterFunctions(sqlite3 *db){

  sqlite3CreateFunc(db, "sqlite_rename_table", 2, SQLITE_UTF8, 0,

                         renameTableFunc, 0, 0);

#ifndef SQLITE_OMIT_TRIGGER

  sqlite3CreateFunc(db, "sqlite_rename_trigger", 2, SQLITE_UTF8, 0,

                         renameTriggerFunc, 0, 0);

#endif

}

/*

** 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 ){

    sqlite3 *db = pParse->db;

    for( pTrig=pTab->pTrigger; pTrig; pTrig=pTrig->pNext ){

      if( pTrig->pSchema==pTempSchema ){

        if( !zWhere ){

          zWhere = sqlite3MPrintf(db, "name=%Q", pTrig->name);

        }else{

          tmp = zWhere;

          zWhere = sqlite3MPrintf(db, "%s OR name=%Q", zWhere, pTrig->name);

          sqlite3DbFree(db, 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;

  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );

  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 );

    sqlite3VdbeAddOp4(v, OP_DropTrigger, iTrigDb, 0, 0, pTrig->name, 0);

  }

#endif

  /* Drop the table and index from the internal schema */

  sqlite3VdbeAddOp4(v, OP_DropTable, iDb, 0, 0, pTab->zName, 0);

  /* Reload the table, index and permanent trigger schemas. */

  zWhere = sqlite3MPrintf(pParse->db, "tbl_name=%Q", zName);

  if( !zWhere ) return;

  sqlite3VdbeAddOp4(v, OP_ParseSchema, iDb, 0, 0, zWhere, P4_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 ){

    sqlite3VdbeAddOp4(v, OP_ParseSchema, 1, 0, 0, zWhere, P4_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( db->mallocFailed ) goto exit_rename_table;

  assert( pSrc->nSrc==1 );

  assert( sqlite3BtreeHoldsAllMutexes(pParse->db) );

  pTab = sqlite3LocateTable(pParse, 0, 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(db, 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

  ** that the table is being renamed to.

  */

  if( strlen(pTab->zName)>6 && 0==sqlite3StrNICmp(pTab->zName, "sqlite_", 7) ){

    sqlite3ErrorMsg(pParse, "table %s may not be altered", pTab->zName);

    goto exit_rename_table;

  }

  if( SQLITE_OK!=sqlite3CheckObjectName(pParse, zName) ){

    goto exit_rename_table;

  }

#ifndef SQLITE_OMIT_VIEW

  if( pTab->pSelect ){

    sqlite3ErrorMsg(pParse, "view %s may not be altered", pTab->zName);

    goto exit_rename_table;

  }

#endif

#ifndef SQLITE_OMIT_AUTHORIZATION

  /* Invoke the authorization callback. */

  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){

    goto exit_rename_table;

  }

#endif

#ifndef SQLITE_OMIT_VIRTUALTABLE

  if( sqlite3ViewGetColumnNames(pParse, pTab) ){

    goto exit_rename_table;

  }

  if( IsVirtual(pTab) && pTab->pMod->pModule->xRename ){

    isVirtualRename = 1;

  }

#endif

  /* Begin a transaction and code the VerifyCookie for database iDb. 

  ** Then modify the schema cookie (since the ALTER TABLE modifies the

  ** schema). Open a statement transaction if the table is a virtual

  ** table.

  */

  v = sqlite3GetVdbe(pParse);

  if( v==0 ){

    goto exit_rename_table;

  }

  sqlite3BeginWriteOperation(pParse, isVirtualRename, iDb);

  sqlite3ChangeCookie(pParse, iDb);

  /* If this is a virtual table, invoke the xRename() function if

  ** one is defined. The xRename() callback will modify the names

  ** of any resources used by the v-table implementation (including other

  ** SQLite tables) that are identified by the name of the virtual table.

  */

#ifndef SQLITE_OMIT_VIRTUALTABLE

  if( isVirtualRename ){

    int i = ++pParse->nMem;

    sqlite3VdbeAddOp4(v, OP_String8, 0, i, 0, zName, 0);

    sqlite3VdbeAddOp4(v, OP_VRename, i, 0, 0,(const char*)pTab->pVtab, P4_VTAB);

  }

#endif

  /* figure out how many UTF-8 characters are in zName */

  zTabName = pTab->zName;

  nTabName = sqlite3Utf8CharLen(zTabName, -1);

  /* Modify the sqlite_master table to use the new table name. */

  sqlite3NestedParse(pParse,

      "UPDATE %Q.%s SET "

#ifdef SQLITE_OMIT_TRIGGER

          "sql = sqlite_rename_table(sql, %Q), "

#else

          "sql = CASE "

            "WHEN type = 'trigger' THEN sqlite_rename_trigger(sql, %Q)"

            "ELSE sqlite_rename_table(sql, %Q) END, "

#endif

          "tbl_name = %Q, "

          "name = CASE "

            "WHEN type='table' THEN %Q "

            "WHEN name LIKE 'sqlite_autoindex%%' AND type='index' THEN "

             "'sqlite_autoindex_' || %Q || substr(name,%d+18) "

            "ELSE name END "

      "WHERE tbl_name=%Q AND "

          "(type='table' OR type='index' OR type='trigger');", 

      zDb, SCHEMA_TABLE(iDb), zName, zName, zName, 

#ifndef SQLITE_OMIT_TRIGGER

      zName,

#endif

      zName, nTabName, zTabName

  );

#ifndef SQLITE_OMIT_AUTOINCREMENT

  /* If the sqlite_sequence table exists in this database, then update 

  ** it with the new table name.

  */

  if( sqlite3FindTable(db, "sqlite_sequence", zDb) ){

    sqlite3NestedParse(pParse,

        "UPDATE \"%w\".sqlite_sequence set name = %Q WHERE name = %Q",

        zDb, zName, pTab->zName);

  }

#endif

#ifndef SQLITE_OMIT_TRIGGER

  /* If there are TEMP triggers on this table, modify the sqlite_temp_master

  ** table. Don't do this if the table being ALTERed is itself located in

  ** the temp database.

  */

  if( (zWhere=whereTempTriggers(pParse, pTab))!=0 ){

    sqlite3NestedParse(pParse, 

        "UPDATE sqlite_temp_master SET "

            "sql = sqlite_rename_trigger(sql, %Q), "

            "tbl_name = %Q "

            "WHERE %s;", zName, zName, zWhere);

    sqlite3DbFree(db, zWhere);

  }

#endif

  /* Drop and reload the internal table schema. */

  reloadTableSchema(pParse, pTab, zName);

exit_rename_table:

  sqlite3SrcListDelete(db, pSrc);

  sqlite3DbFree(db, zName);

}

/*

** This function is called after an "ALTER TABLE ... ADD" statement

** has been parsed. Argument pColDef contains the text of the new

** column definition.

**

** The Table structure pParse->pNewTable was extended to include

** the new column during parsing.

*/

void sqlite3AlterFinishAddColumn(Parse *pParse, Token *pColDef){

  Table *pNew;              /* Copy of pParse->pNewTable */

  Table *pTab;              /* Table being altered */

  int iDb;                  /* Database number */

  const char *zDb;          /* Database name */

  const char *zTab;         /* Table name */

  char *zCol;               /* Null-terminated column definition */

  Column *pCol;             /* The new column */

  Expr *pDflt;              /* Default value for the new column */

  sqlite3 *db;              /* The database connection; */

  if( pParse->nErr ) return;

  pNew = pParse->pNewTable;

  assert( pNew );

  db = pParse->db;

  assert( sqlite3BtreeHoldsAllMutexes(db) );

  iDb = sqlite3SchemaToIndex(db, pNew->pSchema);

  zDb = db->aDb[iDb].zName;

  zTab = pNew->zName;

  pCol = &pNew->aCol[pNew->nCol-1];

  pDflt = pCol->pDflt;

  pTab = sqlite3FindTable(db, zTab, zDb);

  assert( pTab );

#ifndef SQLITE_OMIT_AUTHORIZATION

  /* Invoke the authorization callback. */

  if( sqlite3AuthCheck(pParse, SQLITE_ALTER_TABLE, zDb, pTab->zName, 0) ){

    return;

  }

#endif

  /* If the default value for the new column was specified with a 

  ** literal NULL, then set pDflt to 0. This simplifies checking

  ** for an SQL NULL default below.

  */

  if( pDflt && pDflt->op==TK_NULL ){

    pDflt = 0;

  }

  /* Check that the new column is not specified as PRIMARY KEY or UNIQUE.

  ** If there is a NOT NULL constraint, then the default value for the

  ** column must not be NULL.

  */

  if( pCol->isPrimKey ){

    sqlite3ErrorMsg(pParse, "Cannot add a PRIMARY KEY column");

    return;

  }

  if( pNew->pIndex ){

    sqlite3ErrorMsg(pParse, "Cannot add a UNIQUE column");

    return;

  }

  if( pCol->notNull && !pDflt ){

    sqlite3ErrorMsg(pParse, 

        "Cannot add a NOT NULL column with default value NULL");

    return;

  }

  /* Ensure the default expression is something that sqlite3ValueFromExpr()

  ** can handle (i.e. not CURRENT_TIME etc.)

  */

  if( pDflt ){

    sqlite3_value *pVal;

    if( sqlite3ValueFromExpr(db, pDflt, SQLITE_UTF8, SQLITE_AFF_NONE, &pVal) ){

      db->mallocFailed = 1;

      return;

    }

    if( !pVal ){

      sqlite3ErrorMsg(pParse, "Cannot add a column with non-constant default");

      return;

    }

    sqlite3ValueFree(pVal);

  }

  /* Modify the CREATE TABLE statement. */

  zCol = sqlite3DbStrNDup(db, (char*)pColDef->z, pColDef->n);

  if( zCol ){

    char *zEnd = &zCol[pColDef->n-1];

    while( (zEnd>zCol && *zEnd==';') || isspace(*(unsigned char *)zEnd) ){

      *zEnd-- = '\0';

    }

    sqlite3NestedParse(pParse, 

        "UPDATE \"%w\".%s SET "

          "sql = substr(sql,1,%d) || ', ' || %Q || substr(sql,%d) "

        "WHERE type = 'table' AND name = %Q", 

      zDb, SCHEMA_TABLE(iDb), pNew->addColOffset, zCol, pNew->addColOffset+1,

      zTab

    );

    sqlite3DbFree(db, zCol);

  }

  /* If the default value of the new column is NULL, then set the file

  ** format to 2. If the default value of the new column is not NULL,

  ** the file format becomes 3.

  */

  sqlite3MinimumFileFormat(pParse, iDb, pDflt ? 3 : 2);

  /* Reload the schema of the modified table. */

  reloadTableSchema(pParse, pTab, pTab->zName);

}

/*

** This function is called by the parser after the table-name in

** an "ALTER TABLE <table-name> ADD" statement is parsed. Argument 

** pSrc is the full-name of the table being altered.

**

** This routine makes a (partial) copy of the Table structure

** for the table being altered and sets Parse.pNewTable to point

** to it. Routines called by the parser as the column definition

** is parsed (i.e. sqlite3AddColumn()) add the new Column data to 

** the copy. The copy of the Table structure is deleted by tokenize.c 

** after parsing is finished.

**

** Routine sqlite3AlterFinishAddColumn() will be called to complete

** coding the "ALTER TABLE ... ADD" statement.

*/

void sqlite3AlterBeginAddColumn(Parse *pParse, SrcList *pSrc){

  Table *pNew;

  Table *pTab;

  Vdbe *v;

  int iDb;

  int i;

  int nAlloc;

  sqlite3 *db = pParse->db;

  /* Look up the table being altered. */

  assert( pParse->pNewTable==0 );

  assert( sqlite3BtreeHoldsAllMutexes(db) );

  if( db->mallocFailed ) goto exit_begin_add_column;

  pTab = sqlite3LocateTable(pParse, 0, pSrc->a[0].zName, pSrc->a[0].zDatabase);

  if( !pTab ) goto exit_begin_add_column;

#ifndef SQLITE_OMIT_VIRTUALTABLE

  if( IsVirtual(pTab) ){

    sqlite3ErrorMsg(pParse, "virtual tables may not be altered");

    goto exit_begin_add_column;

  }

#endif

  /* Make sure this is not an attempt to ALTER a view. */

  if( pTab->pSelect ){

    sqlite3ErrorMsg(pParse, "Cannot add a column to a view");

    goto exit_begin_add_column;

  }

  assert( pTab->addColOffset>0 );

  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);

  /* Put a copy of the Table struct in Parse.pNewTable for the

  ** sqlite3AddColumn() function and friends to modify.

  */

  pNew = (Table*)sqlite3DbMallocZero(db, sizeof(Table));

  if( !pNew ) goto exit_begin_add_column;

  pParse->pNewTable = pNew;

  pNew->nRef = 1;

  pNew->db = db;

  pNew->nCol = pTab->nCol;

  assert( pNew->nCol>0 );

  nAlloc = (((pNew->nCol-1)/8)*8)+8;

  assert( nAlloc>=pNew->nCol && nAlloc%8==0 && nAlloc-pNew->nCol<8 );

  pNew->aCol = (Column*)sqlite3DbMallocZero(db, sizeof(Column)*nAlloc);

  pNew->zName = sqlite3DbStrDup(db, pTab->zName);

  if( !pNew->aCol || !pNew->zName ){

    db->mallocFailed = 1;

    goto exit_begin_add_column;

  }

  memcpy(pNew->aCol, pTab->aCol, sizeof(Column)*pNew->nCol);

  for(i=0; i<pNew->nCol; i++){

    Column *pCol = &pNew->aCol[i];

    pCol->zName = sqlite3DbStrDup(db, pCol->zName);

    pCol->zColl = 0;

    pCol->zType = 0;

    pCol->pDflt = 0;

  }

  pNew->pSchema = db->aDb[iDb].pSchema;

  pNew->addColOffset = pTab->addColOffset;

  pNew->nRef = 1;

  /* Begin a transaction and increment the schema cookie.  */

  sqlite3BeginWriteOperation(pParse, 0, iDb);

  v = sqlite3GetVdbe(pParse);

  if( !v ) goto exit_begin_add_column;

  sqlite3ChangeCookie(pParse, iDb);

exit_begin_add_column:

  sqlite3SrcListDelete(db, pSrc);

  return;

}

#endif  /* SQLITE_ALTER_TABLE */