000001  /*
000002  ** 2001 September 15
000003  **
000004  ** The author disclaims copyright to this source code.  In place of
000005  ** a legal notice, here is a blessing:
000006  **
000007  **    May you do good and not evil.
000008  **    May you find forgiveness for yourself and forgive others.
000009  **    May you share freely, never taking more than you give.
000010  **
000011  *************************************************************************
000012  ** This file contains C code routines that are called by the parser
000013  ** in order to generate code for DELETE FROM statements.
000014  */
000015  #include "sqliteInt.h"
000016  
000017  /*
000018  ** While a SrcList can in general represent multiple tables and subqueries
000019  ** (as in the FROM clause of a SELECT statement) in this case it contains
000020  ** the name of a single table, as one might find in an INSERT, DELETE,
000021  ** or UPDATE statement.  Look up that table in the symbol table and
000022  ** return a pointer.  Set an error message and return NULL if the table 
000023  ** name is not found or if any other error occurs.
000024  **
000025  ** The following fields are initialized appropriate in pSrc:
000026  **
000027  **    pSrc->a[0].pTab       Pointer to the Table object
000028  **    pSrc->a[0].pIndex     Pointer to the INDEXED BY index, if there is one
000029  **
000030  */
000031  Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
000032    struct SrcList_item *pItem = pSrc->a;
000033    Table *pTab;
000034    assert( pItem && pSrc->nSrc==1 );
000035    pTab = sqlite3LocateTableItem(pParse, 0, pItem);
000036    sqlite3DeleteTable(pParse->db, pItem->pTab);
000037    pItem->pTab = pTab;
000038    if( pTab ){
000039      pTab->nTabRef++;
000040    }
000041    if( sqlite3IndexedByLookup(pParse, pItem) ){
000042      pTab = 0;
000043    }
000044    return pTab;
000045  }
000046  
000047  /*
000048  ** Check to make sure the given table is writable.  If it is not
000049  ** writable, generate an error message and return 1.  If it is
000050  ** writable return 0;
000051  */
000052  int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
000053    /* A table is not writable under the following circumstances:
000054    **
000055    **   1) It is a virtual table and no implementation of the xUpdate method
000056    **      has been provided, or
000057    **   2) It is a system table (i.e. sqlite_master), this call is not
000058    **      part of a nested parse and writable_schema pragma has not 
000059    **      been specified.
000060    **
000061    ** In either case leave an error message in pParse and return non-zero.
000062    */
000063    if( ( IsVirtual(pTab) 
000064       && sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 )
000065     || ( (pTab->tabFlags & TF_Readonly)!=0
000066       && (pParse->db->flags & SQLITE_WriteSchema)==0
000067       && pParse->nested==0 )
000068    ){
000069      sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
000070      return 1;
000071    }
000072  
000073  #ifndef SQLITE_OMIT_VIEW
000074    if( !viewOk && pTab->pSelect ){
000075      sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
000076      return 1;
000077    }
000078  #endif
000079    return 0;
000080  }
000081  
000082  
000083  #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
000084  /*
000085  ** Evaluate a view and store its result in an ephemeral table.  The
000086  ** pWhere argument is an optional WHERE clause that restricts the
000087  ** set of rows in the view that are to be added to the ephemeral table.
000088  */
000089  void sqlite3MaterializeView(
000090    Parse *pParse,       /* Parsing context */
000091    Table *pView,        /* View definition */
000092    Expr *pWhere,        /* Optional WHERE clause to be added */
000093    ExprList *pOrderBy,  /* Optional ORDER BY clause */
000094    Expr *pLimit,        /* Optional LIMIT clause */
000095    int iCur             /* Cursor number for ephemeral table */
000096  ){
000097    SelectDest dest;
000098    Select *pSel;
000099    SrcList *pFrom;
000100    sqlite3 *db = pParse->db;
000101    int iDb = sqlite3SchemaToIndex(db, pView->pSchema);
000102    pWhere = sqlite3ExprDup(db, pWhere, 0);
000103    pFrom = sqlite3SrcListAppend(db, 0, 0, 0);
000104    if( pFrom ){
000105      assert( pFrom->nSrc==1 );
000106      pFrom->a[0].zName = sqlite3DbStrDup(db, pView->zName);
000107      pFrom->a[0].zDatabase = sqlite3DbStrDup(db, db->aDb[iDb].zDbSName);
000108      assert( pFrom->a[0].pOn==0 );
000109      assert( pFrom->a[0].pUsing==0 );
000110    }
000111    pSel = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, pOrderBy, 
000112                            SF_IncludeHidden, pLimit);
000113    sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
000114    sqlite3Select(pParse, pSel, &dest);
000115    sqlite3SelectDelete(db, pSel);
000116  }
000117  #endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */
000118  
000119  #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
000120  /*
000121  ** Generate an expression tree to implement the WHERE, ORDER BY,
000122  ** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
000123  **
000124  **     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
000125  **                            \__________________________/
000126  **                               pLimitWhere (pInClause)
000127  */
000128  Expr *sqlite3LimitWhere(
000129    Parse *pParse,               /* The parser context */
000130    SrcList *pSrc,               /* the FROM clause -- which tables to scan */
000131    Expr *pWhere,                /* The WHERE clause.  May be null */
000132    ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
000133    Expr *pLimit,                /* The LIMIT clause.  May be null */
000134    char *zStmtType              /* Either DELETE or UPDATE.  For err msgs. */
000135  ){
000136    sqlite3 *db = pParse->db;
000137    Expr *pLhs = NULL;           /* LHS of IN(SELECT...) operator */
000138    Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
000139    ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
000140    SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
000141    Select *pSelect = NULL;      /* Complete SELECT tree */
000142    Table *pTab;
000143  
000144    /* Check that there isn't an ORDER BY without a LIMIT clause.
000145    */
000146    if( pOrderBy && pLimit==0 ) {
000147      sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
000148      sqlite3ExprDelete(pParse->db, pWhere);
000149      sqlite3ExprListDelete(pParse->db, pOrderBy);
000150      return 0;
000151    }
000152  
000153    /* We only need to generate a select expression if there
000154    ** is a limit/offset term to enforce.
000155    */
000156    if( pLimit == 0 ) {
000157      return pWhere;
000158    }
000159  
000160    /* Generate a select expression tree to enforce the limit/offset 
000161    ** term for the DELETE or UPDATE statement.  For example:
000162    **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
000163    ** becomes:
000164    **   DELETE FROM table_a WHERE rowid IN ( 
000165    **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
000166    **   );
000167    */
000168  
000169    pTab = pSrc->a[0].pTab;
000170    if( HasRowid(pTab) ){
000171      pLhs = sqlite3PExpr(pParse, TK_ROW, 0, 0);
000172      pEList = sqlite3ExprListAppend(
000173          pParse, 0, sqlite3PExpr(pParse, TK_ROW, 0, 0)
000174      );
000175    }else{
000176      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
000177      if( pPk->nKeyCol==1 ){
000178        const char *zName = pTab->aCol[pPk->aiColumn[0]].zName;
000179        pLhs = sqlite3Expr(db, TK_ID, zName);
000180        pEList = sqlite3ExprListAppend(pParse, 0, sqlite3Expr(db, TK_ID, zName));
000181      }else{
000182        int i;
000183        for(i=0; i<pPk->nKeyCol; i++){
000184          Expr *p = sqlite3Expr(db, TK_ID, pTab->aCol[pPk->aiColumn[i]].zName);
000185          pEList = sqlite3ExprListAppend(pParse, pEList, p);
000186        }
000187        pLhs = sqlite3PExpr(pParse, TK_VECTOR, 0, 0);
000188        if( pLhs ){
000189          pLhs->x.pList = sqlite3ExprListDup(db, pEList, 0);
000190        }
000191      }
000192    }
000193  
000194    /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
000195    ** and the SELECT subtree. */
000196    pSrc->a[0].pTab = 0;
000197    pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);
000198    pSrc->a[0].pTab = pTab;
000199    pSrc->a[0].pIBIndex = 0;
000200  
000201    /* generate the SELECT expression tree. */
000202    pSelect = sqlite3SelectNew(pParse, pEList, pSelectSrc, pWhere, 0 ,0, 
000203        pOrderBy,0,pLimit
000204    );
000205  
000206    /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
000207    pInClause = sqlite3PExpr(pParse, TK_IN, pLhs, 0);
000208    sqlite3PExprAddSelect(pParse, pInClause, pSelect);
000209    return pInClause;
000210  }
000211  #endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) */
000212         /*      && !defined(SQLITE_OMIT_SUBQUERY) */
000213  
000214  /*
000215  ** Generate code for a DELETE FROM statement.
000216  **
000217  **     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
000218  **                 \________/       \________________/
000219  **                  pTabList              pWhere
000220  */
000221  void sqlite3DeleteFrom(
000222    Parse *pParse,         /* The parser context */
000223    SrcList *pTabList,     /* The table from which we should delete things */
000224    Expr *pWhere,          /* The WHERE clause.  May be null */
000225    ExprList *pOrderBy,    /* ORDER BY clause. May be null */
000226    Expr *pLimit           /* LIMIT clause. May be null */
000227  ){
000228    Vdbe *v;               /* The virtual database engine */
000229    Table *pTab;           /* The table from which records will be deleted */
000230    int i;                 /* Loop counter */
000231    WhereInfo *pWInfo;     /* Information about the WHERE clause */
000232    Index *pIdx;           /* For looping over indices of the table */
000233    int iTabCur;           /* Cursor number for the table */
000234    int iDataCur = 0;      /* VDBE cursor for the canonical data source */
000235    int iIdxCur = 0;       /* Cursor number of the first index */
000236    int nIdx;              /* Number of indices */
000237    sqlite3 *db;           /* Main database structure */
000238    AuthContext sContext;  /* Authorization context */
000239    NameContext sNC;       /* Name context to resolve expressions in */
000240    int iDb;               /* Database number */
000241    int memCnt = 0;        /* Memory cell used for change counting */
000242    int rcauth;            /* Value returned by authorization callback */
000243    int eOnePass;          /* ONEPASS_OFF or _SINGLE or _MULTI */
000244    int aiCurOnePass[2];   /* The write cursors opened by WHERE_ONEPASS */
000245    u8 *aToOpen = 0;       /* Open cursor iTabCur+j if aToOpen[j] is true */
000246    Index *pPk;            /* The PRIMARY KEY index on the table */
000247    int iPk = 0;           /* First of nPk registers holding PRIMARY KEY value */
000248    i16 nPk = 1;           /* Number of columns in the PRIMARY KEY */
000249    int iKey;              /* Memory cell holding key of row to be deleted */
000250    i16 nKey;              /* Number of memory cells in the row key */
000251    int iEphCur = 0;       /* Ephemeral table holding all primary key values */
000252    int iRowSet = 0;       /* Register for rowset of rows to delete */
000253    int addrBypass = 0;    /* Address of jump over the delete logic */
000254    int addrLoop = 0;      /* Top of the delete loop */
000255    int addrEphOpen = 0;   /* Instruction to open the Ephemeral table */
000256    int bComplex;          /* True if there are triggers or FKs or
000257                           ** subqueries in the WHERE clause */
000258   
000259  #ifndef SQLITE_OMIT_TRIGGER
000260    int isView;                  /* True if attempting to delete from a view */
000261    Trigger *pTrigger;           /* List of table triggers, if required */
000262  #endif
000263  
000264    memset(&sContext, 0, sizeof(sContext));
000265    db = pParse->db;
000266    if( pParse->nErr || db->mallocFailed ){
000267      goto delete_from_cleanup;
000268    }
000269    assert( pTabList->nSrc==1 );
000270  
000271  
000272    /* Locate the table which we want to delete.  This table has to be
000273    ** put in an SrcList structure because some of the subroutines we
000274    ** will be calling are designed to work with multiple tables and expect
000275    ** an SrcList* parameter instead of just a Table* parameter.
000276    */
000277    pTab = sqlite3SrcListLookup(pParse, pTabList);
000278    if( pTab==0 )  goto delete_from_cleanup;
000279  
000280    /* Figure out if we have any triggers and if the table being
000281    ** deleted from is a view
000282    */
000283  #ifndef SQLITE_OMIT_TRIGGER
000284    pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
000285    isView = pTab->pSelect!=0;
000286  #else
000287  # define pTrigger 0
000288  # define isView 0
000289  #endif
000290    bComplex = pTrigger || sqlite3FkRequired(pParse, pTab, 0, 0);
000291  #ifdef SQLITE_OMIT_VIEW
000292  # undef isView
000293  # define isView 0
000294  #endif
000295  
000296  #ifdef SQLITE_ENABLE_UPDATE_DELETE_LIMIT
000297    if( !isView ){
000298      pWhere = sqlite3LimitWhere(
000299          pParse, pTabList, pWhere, pOrderBy, pLimit, "DELETE"
000300      );
000301      pOrderBy = 0;
000302      pLimit = 0;
000303    }
000304  #endif
000305  
000306    /* If pTab is really a view, make sure it has been initialized.
000307    */
000308    if( sqlite3ViewGetColumnNames(pParse, pTab) ){
000309      goto delete_from_cleanup;
000310    }
000311  
000312    if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
000313      goto delete_from_cleanup;
000314    }
000315    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
000316    assert( iDb<db->nDb );
000317    rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, 
000318                              db->aDb[iDb].zDbSName);
000319    assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
000320    if( rcauth==SQLITE_DENY ){
000321      goto delete_from_cleanup;
000322    }
000323    assert(!isView || pTrigger);
000324  
000325    /* Assign cursor numbers to the table and all its indices.
000326    */
000327    assert( pTabList->nSrc==1 );
000328    iTabCur = pTabList->a[0].iCursor = pParse->nTab++;
000329    for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){
000330      pParse->nTab++;
000331    }
000332  
000333    /* Start the view context
000334    */
000335    if( isView ){
000336      sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
000337    }
000338  
000339    /* Begin generating code.
000340    */
000341    v = sqlite3GetVdbe(pParse);
000342    if( v==0 ){
000343      goto delete_from_cleanup;
000344    }
000345    if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
000346    sqlite3BeginWriteOperation(pParse, bComplex, iDb);
000347  
000348    /* If we are trying to delete from a view, realize that view into
000349    ** an ephemeral table.
000350    */
000351  #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
000352    if( isView ){
000353      sqlite3MaterializeView(pParse, pTab, 
000354          pWhere, pOrderBy, pLimit, iTabCur
000355      );
000356      iDataCur = iIdxCur = iTabCur;
000357      pOrderBy = 0;
000358      pLimit = 0;
000359    }
000360  #endif
000361  
000362    /* Resolve the column names in the WHERE clause.
000363    */
000364    memset(&sNC, 0, sizeof(sNC));
000365    sNC.pParse = pParse;
000366    sNC.pSrcList = pTabList;
000367    if( sqlite3ResolveExprNames(&sNC, pWhere) ){
000368      goto delete_from_cleanup;
000369    }
000370  
000371    /* Initialize the counter of the number of rows deleted, if
000372    ** we are counting rows.
000373    */
000374    if( (db->flags & SQLITE_CountRows)!=0
000375     && !pParse->nested
000376     && !pParse->pTriggerTab
000377    ){
000378      memCnt = ++pParse->nMem;
000379      sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);
000380    }
000381  
000382  #ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
000383    /* Special case: A DELETE without a WHERE clause deletes everything.
000384    ** It is easier just to erase the whole table. Prior to version 3.6.5,
000385    ** this optimization caused the row change count (the value returned by 
000386    ** API function sqlite3_count_changes) to be set incorrectly.
000387    **
000388    ** The "rcauth==SQLITE_OK" terms is the
000389    ** IMPLEMENTATION-OF: R-17228-37124 If the action code is SQLITE_DELETE and
000390    ** the callback returns SQLITE_IGNORE then the DELETE operation proceeds but
000391    ** the truncate optimization is disabled and all rows are deleted
000392    ** individually.
000393    */
000394    if( rcauth==SQLITE_OK
000395     && pWhere==0
000396     && !bComplex
000397     && !IsVirtual(pTab)
000398  #ifdef SQLITE_ENABLE_PREUPDATE_HOOK
000399     && db->xPreUpdateCallback==0
000400  #endif
000401    ){
000402      assert( !isView );
000403      sqlite3TableLock(pParse, iDb, pTab->tnum, 1, pTab->zName);
000404      if( HasRowid(pTab) ){
000405        sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt ? memCnt : -1,
000406                          pTab->zName, P4_STATIC);
000407      }
000408      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
000409        assert( pIdx->pSchema==pTab->pSchema );
000410        sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
000411      }
000412    }else
000413  #endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
000414    {
000415      u16 wcf = WHERE_ONEPASS_DESIRED|WHERE_DUPLICATES_OK|WHERE_SEEK_TABLE;
000416      if( sNC.ncFlags & NC_VarSelect ) bComplex = 1;
000417      wcf |= (bComplex ? 0 : WHERE_ONEPASS_MULTIROW);
000418      if( HasRowid(pTab) ){
000419        /* For a rowid table, initialize the RowSet to an empty set */
000420        pPk = 0;
000421        nPk = 1;
000422        iRowSet = ++pParse->nMem;
000423        sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
000424      }else{
000425        /* For a WITHOUT ROWID table, create an ephemeral table used to
000426        ** hold all primary keys for rows to be deleted. */
000427        pPk = sqlite3PrimaryKeyIndex(pTab);
000428        assert( pPk!=0 );
000429        nPk = pPk->nKeyCol;
000430        iPk = pParse->nMem+1;
000431        pParse->nMem += nPk;
000432        iEphCur = pParse->nTab++;
000433        addrEphOpen = sqlite3VdbeAddOp2(v, OP_OpenEphemeral, iEphCur, nPk);
000434        sqlite3VdbeSetP4KeyInfo(pParse, pPk);
000435      }
000436    
000437      /* Construct a query to find the rowid or primary key for every row
000438      ** to be deleted, based on the WHERE clause. Set variable eOnePass
000439      ** to indicate the strategy used to implement this delete:
000440      **
000441      **  ONEPASS_OFF:    Two-pass approach - use a FIFO for rowids/PK values.
000442      **  ONEPASS_SINGLE: One-pass approach - at most one row deleted.
000443      **  ONEPASS_MULTI:  One-pass approach - any number of rows may be deleted.
000444      */
000445      pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0, wcf, iTabCur+1);
000446      if( pWInfo==0 ) goto delete_from_cleanup;
000447      eOnePass = sqlite3WhereOkOnePass(pWInfo, aiCurOnePass);
000448      assert( IsVirtual(pTab)==0 || eOnePass!=ONEPASS_MULTI );
000449      assert( IsVirtual(pTab) || bComplex || eOnePass!=ONEPASS_OFF );
000450      if( eOnePass!=ONEPASS_SINGLE ) sqlite3MultiWrite(pParse);
000451    
000452      /* Keep track of the number of rows to be deleted */
000453      if( memCnt ){
000454        sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
000455      }
000456    
000457      /* Extract the rowid or primary key for the current row */
000458      if( pPk ){
000459        for(i=0; i<nPk; i++){
000460          assert( pPk->aiColumn[i]>=0 );
000461          sqlite3ExprCodeGetColumnOfTable(v, pTab, iTabCur,
000462                                          pPk->aiColumn[i], iPk+i);
000463        }
000464        iKey = iPk;
000465      }else{
000466        iKey = pParse->nMem + 1;
000467        iKey = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iTabCur, iKey, 0);
000468        if( iKey>pParse->nMem ) pParse->nMem = iKey;
000469      }
000470    
000471      if( eOnePass!=ONEPASS_OFF ){
000472        /* For ONEPASS, no need to store the rowid/primary-key. There is only
000473        ** one, so just keep it in its register(s) and fall through to the
000474        ** delete code.  */
000475        nKey = nPk; /* OP_Found will use an unpacked key */
000476        aToOpen = sqlite3DbMallocRawNN(db, nIdx+2);
000477        if( aToOpen==0 ){
000478          sqlite3WhereEnd(pWInfo);
000479          goto delete_from_cleanup;
000480        }
000481        memset(aToOpen, 1, nIdx+1);
000482        aToOpen[nIdx+1] = 0;
000483        if( aiCurOnePass[0]>=0 ) aToOpen[aiCurOnePass[0]-iTabCur] = 0;
000484        if( aiCurOnePass[1]>=0 ) aToOpen[aiCurOnePass[1]-iTabCur] = 0;
000485        if( addrEphOpen ) sqlite3VdbeChangeToNoop(v, addrEphOpen);
000486      }else{
000487        if( pPk ){
000488          /* Add the PK key for this row to the temporary table */
000489          iKey = ++pParse->nMem;
000490          nKey = 0;   /* Zero tells OP_Found to use a composite key */
000491          sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, iKey,
000492              sqlite3IndexAffinityStr(pParse->db, pPk), nPk);
000493          sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEphCur, iKey, iPk, nPk);
000494        }else{
000495          /* Add the rowid of the row to be deleted to the RowSet */
000496          nKey = 1;  /* OP_DeferredSeek always uses a single rowid */
000497          sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);
000498        }
000499      }
000500    
000501      /* If this DELETE cannot use the ONEPASS strategy, this is the 
000502      ** end of the WHERE loop */
000503      if( eOnePass!=ONEPASS_OFF ){
000504        addrBypass = sqlite3VdbeMakeLabel(v);
000505      }else{
000506        sqlite3WhereEnd(pWInfo);
000507      }
000508    
000509      /* Unless this is a view, open cursors for the table we are 
000510      ** deleting from and all its indices. If this is a view, then the
000511      ** only effect this statement has is to fire the INSTEAD OF 
000512      ** triggers.
000513      */
000514      if( !isView ){
000515        int iAddrOnce = 0;
000516        if( eOnePass==ONEPASS_MULTI ){
000517          iAddrOnce = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
000518        }
000519        testcase( IsVirtual(pTab) );
000520        sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, OPFLAG_FORDELETE,
000521                                   iTabCur, aToOpen, &iDataCur, &iIdxCur);
000522        assert( pPk || IsVirtual(pTab) || iDataCur==iTabCur );
000523        assert( pPk || IsVirtual(pTab) || iIdxCur==iDataCur+1 );
000524        if( eOnePass==ONEPASS_MULTI ) sqlite3VdbeJumpHere(v, iAddrOnce);
000525      }
000526    
000527      /* Set up a loop over the rowids/primary-keys that were found in the
000528      ** where-clause loop above.
000529      */
000530      if( eOnePass!=ONEPASS_OFF ){
000531        assert( nKey==nPk );  /* OP_Found will use an unpacked key */
000532        if( !IsVirtual(pTab) && aToOpen[iDataCur-iTabCur] ){
000533          assert( pPk!=0 || pTab->pSelect!=0 );
000534          sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, addrBypass, iKey, nKey);
000535          VdbeCoverage(v);
000536        }
000537      }else if( pPk ){
000538        addrLoop = sqlite3VdbeAddOp1(v, OP_Rewind, iEphCur); VdbeCoverage(v);
000539        if( IsVirtual(pTab) ){
000540          sqlite3VdbeAddOp3(v, OP_Column, iEphCur, 0, iKey);
000541        }else{
000542          sqlite3VdbeAddOp2(v, OP_RowData, iEphCur, iKey);
000543        }
000544        assert( nKey==0 );  /* OP_Found will use a composite key */
000545      }else{
000546        addrLoop = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, 0, iKey);
000547        VdbeCoverage(v);
000548        assert( nKey==1 );
000549      }  
000550    
000551      /* Delete the row */
000552  #ifndef SQLITE_OMIT_VIRTUALTABLE
000553      if( IsVirtual(pTab) ){
000554        const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
000555        sqlite3VtabMakeWritable(pParse, pTab);
000556        assert( eOnePass==ONEPASS_OFF || eOnePass==ONEPASS_SINGLE );
000557        sqlite3MayAbort(pParse);
000558        if( eOnePass==ONEPASS_SINGLE ){
000559          sqlite3VdbeAddOp1(v, OP_Close, iTabCur);
000560          if( sqlite3IsToplevel(pParse) ){
000561            pParse->isMultiWrite = 0;
000562          }
000563        }
000564        sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iKey, pVTab, P4_VTAB);
000565        sqlite3VdbeChangeP5(v, OE_Abort);
000566      }else
000567  #endif
000568      {
000569        int count = (pParse->nested==0);    /* True to count changes */
000570        sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
000571            iKey, nKey, count, OE_Default, eOnePass, aiCurOnePass[1]);
000572      }
000573    
000574      /* End of the loop over all rowids/primary-keys. */
000575      if( eOnePass!=ONEPASS_OFF ){
000576        sqlite3VdbeResolveLabel(v, addrBypass);
000577        sqlite3WhereEnd(pWInfo);
000578      }else if( pPk ){
000579        sqlite3VdbeAddOp2(v, OP_Next, iEphCur, addrLoop+1); VdbeCoverage(v);
000580        sqlite3VdbeJumpHere(v, addrLoop);
000581      }else{
000582        sqlite3VdbeGoto(v, addrLoop);
000583        sqlite3VdbeJumpHere(v, addrLoop);
000584      }     
000585    } /* End non-truncate path */
000586  
000587    /* Update the sqlite_sequence table by storing the content of the
000588    ** maximum rowid counter values recorded while inserting into
000589    ** autoincrement tables.
000590    */
000591    if( pParse->nested==0 && pParse->pTriggerTab==0 ){
000592      sqlite3AutoincrementEnd(pParse);
000593    }
000594  
000595    /* Return the number of rows that were deleted. If this routine is 
000596    ** generating code because of a call to sqlite3NestedParse(), do not
000597    ** invoke the callback function.
000598    */
000599    if( memCnt ){
000600      sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);
000601      sqlite3VdbeSetNumCols(v, 1);
000602      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
000603    }
000604  
000605  delete_from_cleanup:
000606    sqlite3AuthContextPop(&sContext);
000607    sqlite3SrcListDelete(db, pTabList);
000608    sqlite3ExprDelete(db, pWhere);
000609  #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) 
000610    sqlite3ExprListDelete(db, pOrderBy);
000611    sqlite3ExprDelete(db, pLimit);
000612  #endif
000613    sqlite3DbFree(db, aToOpen);
000614    return;
000615  }
000616  /* Make sure "isView" and other macros defined above are undefined. Otherwise
000617  ** they may interfere with compilation of other functions in this file
000618  ** (or in another file, if this file becomes part of the amalgamation).  */
000619  #ifdef isView
000620   #undef isView
000621  #endif
000622  #ifdef pTrigger
000623   #undef pTrigger
000624  #endif
000625  
000626  /*
000627  ** This routine generates VDBE code that causes a single row of a
000628  ** single table to be deleted.  Both the original table entry and
000629  ** all indices are removed.
000630  **
000631  ** Preconditions:
000632  **
000633  **   1.  iDataCur is an open cursor on the btree that is the canonical data
000634  **       store for the table.  (This will be either the table itself,
000635  **       in the case of a rowid table, or the PRIMARY KEY index in the case
000636  **       of a WITHOUT ROWID table.)
000637  **
000638  **   2.  Read/write cursors for all indices of pTab must be open as
000639  **       cursor number iIdxCur+i for the i-th index.
000640  **
000641  **   3.  The primary key for the row to be deleted must be stored in a
000642  **       sequence of nPk memory cells starting at iPk.  If nPk==0 that means
000643  **       that a search record formed from OP_MakeRecord is contained in the
000644  **       single memory location iPk.
000645  **
000646  ** eMode:
000647  **   Parameter eMode may be passed either ONEPASS_OFF (0), ONEPASS_SINGLE, or
000648  **   ONEPASS_MULTI.  If eMode is not ONEPASS_OFF, then the cursor
000649  **   iDataCur already points to the row to delete. If eMode is ONEPASS_OFF
000650  **   then this function must seek iDataCur to the entry identified by iPk
000651  **   and nPk before reading from it.
000652  **
000653  **   If eMode is ONEPASS_MULTI, then this call is being made as part
000654  **   of a ONEPASS delete that affects multiple rows. In this case, if 
000655  **   iIdxNoSeek is a valid cursor number (>=0) and is not the same as
000656  **   iDataCur, then its position should be preserved following the delete
000657  **   operation. Or, if iIdxNoSeek is not a valid cursor number, the
000658  **   position of iDataCur should be preserved instead.
000659  **
000660  ** iIdxNoSeek:
000661  **   If iIdxNoSeek is a valid cursor number (>=0) not equal to iDataCur,
000662  **   then it identifies an index cursor (from within array of cursors
000663  **   starting at iIdxCur) that already points to the index entry to be deleted.
000664  **   Except, this optimization is disabled if there are BEFORE triggers since
000665  **   the trigger body might have moved the cursor.
000666  */
000667  void sqlite3GenerateRowDelete(
000668    Parse *pParse,     /* Parsing context */
000669    Table *pTab,       /* Table containing the row to be deleted */
000670    Trigger *pTrigger, /* List of triggers to (potentially) fire */
000671    int iDataCur,      /* Cursor from which column data is extracted */
000672    int iIdxCur,       /* First index cursor */
000673    int iPk,           /* First memory cell containing the PRIMARY KEY */
000674    i16 nPk,           /* Number of PRIMARY KEY memory cells */
000675    u8 count,          /* If non-zero, increment the row change counter */
000676    u8 onconf,         /* Default ON CONFLICT policy for triggers */
000677    u8 eMode,          /* ONEPASS_OFF, _SINGLE, or _MULTI.  See above */
000678    int iIdxNoSeek     /* Cursor number of cursor that does not need seeking */
000679  ){
000680    Vdbe *v = pParse->pVdbe;        /* Vdbe */
000681    int iOld = 0;                   /* First register in OLD.* array */
000682    int iLabel;                     /* Label resolved to end of generated code */
000683    u8 opSeek;                      /* Seek opcode */
000684  
000685    /* Vdbe is guaranteed to have been allocated by this stage. */
000686    assert( v );
000687    VdbeModuleComment((v, "BEGIN: GenRowDel(%d,%d,%d,%d)",
000688                           iDataCur, iIdxCur, iPk, (int)nPk));
000689  
000690    /* Seek cursor iCur to the row to delete. If this row no longer exists 
000691    ** (this can happen if a trigger program has already deleted it), do
000692    ** not attempt to delete it or fire any DELETE triggers.  */
000693    iLabel = sqlite3VdbeMakeLabel(v);
000694    opSeek = HasRowid(pTab) ? OP_NotExists : OP_NotFound;
000695    if( eMode==ONEPASS_OFF ){
000696      sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
000697      VdbeCoverageIf(v, opSeek==OP_NotExists);
000698      VdbeCoverageIf(v, opSeek==OP_NotFound);
000699    }
000700   
000701    /* If there are any triggers to fire, allocate a range of registers to
000702    ** use for the old.* references in the triggers.  */
000703    if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){
000704      u32 mask;                     /* Mask of OLD.* columns in use */
000705      int iCol;                     /* Iterator used while populating OLD.* */
000706      int addrStart;                /* Start of BEFORE trigger programs */
000707  
000708      /* TODO: Could use temporary registers here. Also could attempt to
000709      ** avoid copying the contents of the rowid register.  */
000710      mask = sqlite3TriggerColmask(
000711          pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf
000712      );
000713      mask |= sqlite3FkOldmask(pParse, pTab);
000714      iOld = pParse->nMem+1;
000715      pParse->nMem += (1 + pTab->nCol);
000716  
000717      /* Populate the OLD.* pseudo-table register array. These values will be 
000718      ** used by any BEFORE and AFTER triggers that exist.  */
000719      sqlite3VdbeAddOp2(v, OP_Copy, iPk, iOld);
000720      for(iCol=0; iCol<pTab->nCol; iCol++){
000721        testcase( mask!=0xffffffff && iCol==31 );
000722        testcase( mask!=0xffffffff && iCol==32 );
000723        if( mask==0xffffffff || (iCol<=31 && (mask & MASKBIT32(iCol))!=0) ){
000724          sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, iCol, iOld+iCol+1);
000725        }
000726      }
000727  
000728      /* Invoke BEFORE DELETE trigger programs. */
000729      addrStart = sqlite3VdbeCurrentAddr(v);
000730      sqlite3CodeRowTrigger(pParse, pTrigger, 
000731          TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
000732      );
000733  
000734      /* If any BEFORE triggers were coded, then seek the cursor to the 
000735      ** row to be deleted again. It may be that the BEFORE triggers moved
000736      ** the cursor or already deleted the row that the cursor was
000737      ** pointing to.
000738      **
000739      ** Also disable the iIdxNoSeek optimization since the BEFORE trigger
000740      ** may have moved that cursor.
000741      */
000742      if( addrStart<sqlite3VdbeCurrentAddr(v) ){
000743        sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
000744        VdbeCoverageIf(v, opSeek==OP_NotExists);
000745        VdbeCoverageIf(v, opSeek==OP_NotFound);
000746        testcase( iIdxNoSeek>=0 );
000747        iIdxNoSeek = -1;
000748      }
000749  
000750      /* Do FK processing. This call checks that any FK constraints that
000751      ** refer to this table (i.e. constraints attached to other tables) 
000752      ** are not violated by deleting this row.  */
000753      sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);
000754    }
000755  
000756    /* Delete the index and table entries. Skip this step if pTab is really
000757    ** a view (in which case the only effect of the DELETE statement is to
000758    ** fire the INSTEAD OF triggers).  
000759    **
000760    ** If variable 'count' is non-zero, then this OP_Delete instruction should
000761    ** invoke the update-hook. The pre-update-hook, on the other hand should
000762    ** be invoked unless table pTab is a system table. The difference is that
000763    ** the update-hook is not invoked for rows removed by REPLACE, but the 
000764    ** pre-update-hook is.
000765    */ 
000766    if( pTab->pSelect==0 ){
000767      u8 p5 = 0;
000768      sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);
000769      sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));
000770      if( pParse->nested==0 || 0==sqlite3_stricmp(pTab->zName, "sqlite_stat1") ){
000771        sqlite3VdbeAppendP4(v, (char*)pTab, P4_TABLE);
000772      }
000773      if( eMode!=ONEPASS_OFF ){
000774        sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);
000775      }
000776      if( iIdxNoSeek>=0 && iIdxNoSeek!=iDataCur ){
000777        sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);
000778      }
000779      if( eMode==ONEPASS_MULTI ) p5 |= OPFLAG_SAVEPOSITION;
000780      sqlite3VdbeChangeP5(v, p5);
000781    }
000782  
000783    /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
000784    ** handle rows (possibly in other tables) that refer via a foreign key
000785    ** to the row just deleted. */ 
000786    sqlite3FkActions(pParse, pTab, 0, iOld, 0, 0);
000787  
000788    /* Invoke AFTER DELETE trigger programs. */
000789    sqlite3CodeRowTrigger(pParse, pTrigger, 
000790        TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel
000791    );
000792  
000793    /* Jump here if the row had already been deleted before any BEFORE
000794    ** trigger programs were invoked. Or if a trigger program throws a 
000795    ** RAISE(IGNORE) exception.  */
000796    sqlite3VdbeResolveLabel(v, iLabel);
000797    VdbeModuleComment((v, "END: GenRowDel()"));
000798  }
000799  
000800  /*
000801  ** This routine generates VDBE code that causes the deletion of all
000802  ** index entries associated with a single row of a single table, pTab
000803  **
000804  ** Preconditions:
000805  **
000806  **   1.  A read/write cursor "iDataCur" must be open on the canonical storage
000807  **       btree for the table pTab.  (This will be either the table itself
000808  **       for rowid tables or to the primary key index for WITHOUT ROWID
000809  **       tables.)
000810  **
000811  **   2.  Read/write cursors for all indices of pTab must be open as
000812  **       cursor number iIdxCur+i for the i-th index.  (The pTab->pIndex
000813  **       index is the 0-th index.)
000814  **
000815  **   3.  The "iDataCur" cursor must be already be positioned on the row
000816  **       that is to be deleted.
000817  */
000818  void sqlite3GenerateRowIndexDelete(
000819    Parse *pParse,     /* Parsing and code generating context */
000820    Table *pTab,       /* Table containing the row to be deleted */
000821    int iDataCur,      /* Cursor of table holding data. */
000822    int iIdxCur,       /* First index cursor */
000823    int *aRegIdx,      /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */
000824    int iIdxNoSeek     /* Do not delete from this cursor */
000825  ){
000826    int i;             /* Index loop counter */
000827    int r1 = -1;       /* Register holding an index key */
000828    int iPartIdxLabel; /* Jump destination for skipping partial index entries */
000829    Index *pIdx;       /* Current index */
000830    Index *pPrior = 0; /* Prior index */
000831    Vdbe *v;           /* The prepared statement under construction */
000832    Index *pPk;        /* PRIMARY KEY index, or NULL for rowid tables */
000833  
000834    v = pParse->pVdbe;
000835    pPk = HasRowid(pTab) ? 0 : sqlite3PrimaryKeyIndex(pTab);
000836    for(i=0, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
000837      assert( iIdxCur+i!=iDataCur || pPk==pIdx );
000838      if( aRegIdx!=0 && aRegIdx[i]==0 ) continue;
000839      if( pIdx==pPk ) continue;
000840      if( iIdxCur+i==iIdxNoSeek ) continue;
000841      VdbeModuleComment((v, "GenRowIdxDel for %s", pIdx->zName));
000842      r1 = sqlite3GenerateIndexKey(pParse, pIdx, iDataCur, 0, 1,
000843          &iPartIdxLabel, pPrior, r1);
000844      sqlite3VdbeAddOp3(v, OP_IdxDelete, iIdxCur+i, r1,
000845          pIdx->uniqNotNull ? pIdx->nKeyCol : pIdx->nColumn);
000846      sqlite3ResolvePartIdxLabel(pParse, iPartIdxLabel);
000847      pPrior = pIdx;
000848    }
000849  }
000850  
000851  /*
000852  ** Generate code that will assemble an index key and stores it in register
000853  ** regOut.  The key with be for index pIdx which is an index on pTab.
000854  ** iCur is the index of a cursor open on the pTab table and pointing to
000855  ** the entry that needs indexing.  If pTab is a WITHOUT ROWID table, then
000856  ** iCur must be the cursor of the PRIMARY KEY index.
000857  **
000858  ** Return a register number which is the first in a block of
000859  ** registers that holds the elements of the index key.  The
000860  ** block of registers has already been deallocated by the time
000861  ** this routine returns.
000862  **
000863  ** If *piPartIdxLabel is not NULL, fill it in with a label and jump
000864  ** to that label if pIdx is a partial index that should be skipped.
000865  ** The label should be resolved using sqlite3ResolvePartIdxLabel().
000866  ** A partial index should be skipped if its WHERE clause evaluates
000867  ** to false or null.  If pIdx is not a partial index, *piPartIdxLabel
000868  ** will be set to zero which is an empty label that is ignored by
000869  ** sqlite3ResolvePartIdxLabel().
000870  **
000871  ** The pPrior and regPrior parameters are used to implement a cache to
000872  ** avoid unnecessary register loads.  If pPrior is not NULL, then it is
000873  ** a pointer to a different index for which an index key has just been
000874  ** computed into register regPrior.  If the current pIdx index is generating
000875  ** its key into the same sequence of registers and if pPrior and pIdx share
000876  ** a column in common, then the register corresponding to that column already
000877  ** holds the correct value and the loading of that register is skipped.
000878  ** This optimization is helpful when doing a DELETE or an INTEGRITY_CHECK 
000879  ** on a table with multiple indices, and especially with the ROWID or
000880  ** PRIMARY KEY columns of the index.
000881  */
000882  int sqlite3GenerateIndexKey(
000883    Parse *pParse,       /* Parsing context */
000884    Index *pIdx,         /* The index for which to generate a key */
000885    int iDataCur,        /* Cursor number from which to take column data */
000886    int regOut,          /* Put the new key into this register if not 0 */
000887    int prefixOnly,      /* Compute only a unique prefix of the key */
000888    int *piPartIdxLabel, /* OUT: Jump to this label to skip partial index */
000889    Index *pPrior,       /* Previously generated index key */
000890    int regPrior         /* Register holding previous generated key */
000891  ){
000892    Vdbe *v = pParse->pVdbe;
000893    int j;
000894    int regBase;
000895    int nCol;
000896  
000897    if( piPartIdxLabel ){
000898      if( pIdx->pPartIdxWhere ){
000899        *piPartIdxLabel = sqlite3VdbeMakeLabel(v);
000900        pParse->iSelfTab = iDataCur + 1;
000901        sqlite3ExprCachePush(pParse);
000902        sqlite3ExprIfFalseDup(pParse, pIdx->pPartIdxWhere, *piPartIdxLabel, 
000903                              SQLITE_JUMPIFNULL);
000904        pParse->iSelfTab = 0;
000905      }else{
000906        *piPartIdxLabel = 0;
000907      }
000908    }
000909    nCol = (prefixOnly && pIdx->uniqNotNull) ? pIdx->nKeyCol : pIdx->nColumn;
000910    regBase = sqlite3GetTempRange(pParse, nCol);
000911    if( pPrior && (regBase!=regPrior || pPrior->pPartIdxWhere) ) pPrior = 0;
000912    for(j=0; j<nCol; j++){
000913      if( pPrior
000914       && pPrior->aiColumn[j]==pIdx->aiColumn[j]
000915       && pPrior->aiColumn[j]!=XN_EXPR
000916      ){
000917        /* This column was already computed by the previous index */
000918        continue;
000919      }
000920      sqlite3ExprCodeLoadIndexColumn(pParse, pIdx, iDataCur, j, regBase+j);
000921      /* If the column affinity is REAL but the number is an integer, then it
000922      ** might be stored in the table as an integer (using a compact
000923      ** representation) then converted to REAL by an OP_RealAffinity opcode.
000924      ** But we are getting ready to store this value back into an index, where
000925      ** it should be converted by to INTEGER again.  So omit the OP_RealAffinity
000926      ** opcode if it is present */
000927      sqlite3VdbeDeletePriorOpcode(v, OP_RealAffinity);
000928    }
000929    if( regOut ){
000930      sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol, regOut);
000931      if( pIdx->pTable->pSelect ){
000932        const char *zAff = sqlite3IndexAffinityStr(pParse->db, pIdx);
000933        sqlite3VdbeChangeP4(v, -1, zAff, P4_TRANSIENT);
000934      }
000935    }
000936    sqlite3ReleaseTempRange(pParse, regBase, nCol);
000937    return regBase;
000938  }
000939  
000940  /*
000941  ** If a prior call to sqlite3GenerateIndexKey() generated a jump-over label
000942  ** because it was a partial index, then this routine should be called to
000943  ** resolve that label.
000944  */
000945  void sqlite3ResolvePartIdxLabel(Parse *pParse, int iLabel){
000946    if( iLabel ){
000947      sqlite3VdbeResolveLabel(pParse->pVdbe, iLabel);
000948      sqlite3ExprCachePop(pParse);
000949    }
000950  }