delete.c

sqlite的最新源码 This ZIP archive contains preprocessed C code for the SQLite library as individual sour

/*
** 2001 September 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 are called by the parser
** in order to generate code for DELETE FROM statements.
**
** $Id: delete.c,v 1.187 2008/11/19 09:05:27 danielk1977 Exp $
*/
#include "sqliteInt.h"

/*
** Look up every table that is named in pSrc.  If any table is not found,
** add an error message to pParse->zErrMsg and return NULL.  If all tables
** are found, return a pointer to the last table.
*/
Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
  struct SrcList_item *pItem = pSrc->a;
  Table *pTab;
  assert( pItem && pSrc->nSrc==1 );
  pTab = sqlite3LocateTable(pParse, 0, pItem->zName, pItem->zDatabase);
  sqlite3DeleteTable(pItem->pTab);
  pItem->pTab = pTab;
  if( pTab ){
    pTab->nRef++;
  }
  if( sqlite3IndexedByLookup(pParse, pItem) ){
    pTab = 0;
  }
  return pTab;
}

/*
** Check to make sure the given table is writable.  If it is not
** writable, generate an error message and return 1.  If it is
** writable return 0;
*/
int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
  if( ((pTab->tabFlags & TF_Readonly)!=0
        && (pParse->db->flags & SQLITE_WriteSchema)==0
        && pParse->nested==0) 
#ifndef SQLITE_OMIT_VIRTUALTABLE
      || (pTab->pMod && pTab->pMod->pModule->xUpdate==0)
#endif
  ){
    sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
    return 1;
  }
#ifndef SQLITE_OMIT_VIEW
  if( !viewOk && pTab->pSelect ){
    sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
    return 1;
  }
#endif
  return 0;
}

/*
** Generate code that will open a table for reading.
*/
void sqlite3OpenTable(
  Parse *p,       /* Generate code into this VDBE */
  int iCur,       /* The cursor number of the table */
  int iDb,        /* The database index in sqlite3.aDb[] */
  Table *pTab,    /* The table to be opened */
  int opcode      /* OP_OpenRead or OP_OpenWrite */
){
  Vdbe *v;
  if( IsVirtual(pTab) ) return;
  v = sqlite3GetVdbe(p);
  assert( opcode==OP_OpenWrite || opcode==OP_OpenRead );
  sqlite3TableLock(p, iDb, pTab->tnum, (opcode==OP_OpenWrite), pTab->zName);
  sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
  sqlite3VdbeAddOp3(v, opcode, iCur, pTab->tnum, iDb);
  VdbeComment((v, "%s", pTab->zName));
}


#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
/*
** Evaluate a view and store its result in an ephemeral table.  The
** pWhere argument is an optional WHERE clause that restricts the
** set of rows in the view that are to be added to the ephemeral table.
*/
void sqlite3MaterializeView(
  Parse *pParse,       /* Parsing context */
  Table *pView,        /* View definition */
  Expr *pWhere,        /* Optional WHERE clause to be added */
  int iCur             /* Cursor number for ephemerial table */
){
  SelectDest dest;
  Select *pDup;
  sqlite3 *db = pParse->db;

  pDup = sqlite3SelectDup(db, pView->pSelect);
  if( pWhere ){
    SrcList *pFrom;
    Token viewName;
    
    pWhere = sqlite3ExprDup(db, pWhere);
    viewName.z = (u8*)pView->zName;
    viewName.n = (unsigned int)strlen((const char*)viewName.z);
    pFrom = sqlite3SrcListAppendFromTerm(pParse, 0, 0, 0, &viewName, pDup, 0,0);
    pDup = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0, 0, 0, 0);
  }
  sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
  sqlite3Select(pParse, pDup, &dest);
  sqlite3SelectDelete(db, pDup);
}
#endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */

#if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
/*
** Generate an expression tree to implement the WHERE, ORDER BY,
** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
**
**     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
**                            \__________________________/
**                               pLimitWhere (pInClause)
*/
Expr *sqlite3LimitWhere(
  Parse *pParse,               /* The parser context */
  SrcList *pSrc,               /* the FROM clause -- which tables to scan */
  Expr *pWhere,                /* The WHERE clause.  May be null */
  ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
  Expr *pLimit,                /* The LIMIT clause.  May be null */
  Expr *pOffset,               /* The OFFSET clause.  May be null */
  char *zStmtType              /* Either DELETE or UPDATE.  For error messages. */
){
  Expr *pWhereRowid = NULL;    /* WHERE rowid .. */
  Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
  Expr *pSelectRowid = NULL;   /* SELECT rowid ... */
  ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
  SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
  Select *pSelect = NULL;      /* Complete SELECT tree */

  /* Check that there isn't an ORDER BY without a LIMIT clause.
  */
  if( pOrderBy && (pLimit == 0) ) {
    sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
    pParse->parseError = 1;
    goto limit_where_cleanup_2;
  }

  /* We only need to generate a select expression if there
  ** is a limit/offset term to enforce.
  */
  if( pLimit == 0 ) {
    /* if pLimit is null, pOffset will always be null as well. */
    assert( pOffset == 0 );
    return pWhere;
  }

  /* Generate a select expression tree to enforce the limit/offset 
  ** term for the DELETE or UPDATE statement.  For example:
  **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
  ** becomes:
  **   DELETE FROM table_a WHERE rowid IN ( 
  **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
  **   );
  */

  pSelectRowid = sqlite3Expr(pParse->db, TK_ROW, 0, 0, 0);
  if( pSelectRowid == 0 ) goto limit_where_cleanup_2;
  pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid, 0);
  if( pEList == 0 ) goto limit_where_cleanup_2;

  /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
  ** and the SELECT subtree. */
  pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc);
  if( pSelectSrc == 0 ) {
    sqlite3ExprListDelete(pParse->db, pEList);
    goto limit_where_cleanup_2;
  }

  /* generate the SELECT expression tree. */
  pSelect = sqlite3SelectNew(pParse,pEList,pSelectSrc,pWhere,0,0,pOrderBy,0,pLimit,pOffset);
  if( pSelect == 0 ) return 0;

  /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
  pWhereRowid = sqlite3Expr(pParse->db, TK_ROW, 0, 0, 0);
  if( pWhereRowid == 0 ) goto limit_where_cleanup_1;
  pInClause = sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0, 0);
  if( pInClause == 0 ) goto limit_where_cleanup_1;

  pInClause->pSelect = pSelect;
  sqlite3ExprSetHeight(pParse, pInClause);
  return pInClause;

  /* something went wrong. clean up anything allocated. */
limit_where_cleanup_1:
  sqlite3SelectDelete(pParse->db, pSelect);
  return 0;

limit_where_cleanup_2:
  sqlite3ExprDelete(pParse->db, pWhere);
  sqlite3ExprListDelete(pParse->db, pOrderBy);
  sqlite3ExprDelete(pParse->db, pLimit);
  sqlite3ExprDelete(pParse->db, pOffset);
  return 0;
}
#endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY) */

/*
** Generate code for a DELETE FROM statement.
**
**     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
**                 \________/       \________________/
**                  pTabList              pWhere
*/
void sqlite3DeleteFrom(
  Parse *pParse,         /* The parser context */
  SrcList *pTabList,     /* The table from which we should delete things */
  Expr *pWhere           /* The WHERE clause.  May be null */
){
  Vdbe *v;               /* The virtual database engine */
  Table *pTab;           /* The table from which records will be deleted */
  const char *zDb;       /* Name of database holding pTab */
  int end, addr = 0;     /* A couple addresses of generated code */
  int i;                 /* Loop counter */
  WhereInfo *pWInfo;     /* Information about the WHERE clause */
  Index *pIdx;           /* For looping over indices of the table */
  int iCur;              /* VDBE Cursor number for pTab */
  sqlite3 *db;           /* Main database structure */
  AuthContext sContext;  /* Authorization context */
  int oldIdx = -1;       /* Cursor for the OLD table of AFTER triggers */
  NameContext sNC;       /* Name context to resolve expressions in */
  int iDb;               /* Database number */
  int memCnt = -1;       /* Memory cell used for change counting */
  int rcauth;            /* Value returned by authorization callback */

#ifndef SQLITE_OMIT_TRIGGER
  int isView;                  /* True if attempting to delete from a view */
  int triggers_exist = 0;      /* True if any triggers exist */
#endif
  int iBeginAfterTrigger;      /* Address of after trigger program */
  int iEndAfterTrigger;        /* Exit of after trigger program */
  int iBeginBeforeTrigger;     /* Address of before trigger program */
  int iEndBeforeTrigger;       /* Exit of before trigger program */
  u32 old_col_mask = 0;        /* Mask of OLD.* columns in use */

  sContext.pParse = 0;
  db = pParse->db;
  if( pParse->nErr || db->mallocFailed ){
    goto delete_from_cleanup;
  }
  assert( pTabList->nSrc==1 );

  /* Locate the table which we want to delete.  This table has to be
  ** put in an SrcList structure because some of the subroutines we
  ** will be calling are designed to work with multiple tables and expect
  ** an SrcList* parameter instead of just a Table* parameter.
  */
  pTab = sqlite3SrcListLookup(pParse, pTabList);
  if( pTab==0 )  goto delete_from_cleanup;

  /* Figure out if we have any triggers and if the table being
  ** deleted from is a view
  */
#ifndef SQLITE_OMIT_TRIGGER
  triggers_exist = sqlite3TriggersExist(pTab, TK_DELETE, 0);
  isView = pTab->pSelect!=0;
#else
# define triggers_exist 0
# define isView 0
#endif
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif

  if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
    goto delete_from_cleanup;
  }
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb<db->nDb );
  zDb = db->aDb[iDb].zName;
  rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb);
  assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
  if( rcauth==SQLITE_DENY ){
    goto delete_from_cleanup;
  }
  assert(!isView || triggers_exist);

  /* If pTab is really a view, make sure it has been initialized.
  */
  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto delete_from_cleanup;
  }

  /* Allocate a cursor used to store the old.* data for a trigger.
  */
  if( triggers_exist ){ 
    oldIdx = pParse->nTab++;
  }

  /* Assign  cursor number to the table and all its indices.
  */
  assert( pTabList->nSrc==1 );
  iCur = pTabList->a[0].iCursor = pParse->nTab++;
  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
    pParse->nTab++;
  }

  /* Start the view context
  */
  if( isView ){
    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
  }

  /* Begin generating code.