SQLite

**
** If the BTREE_SAVEPOSITION bit of the flags parameter is zero, then
** the cursor is left pointing at an arbitrary location after the delete.
** But if that bit is set, then the cursor is left in a state such that
** the next call to BtreeNext() or BtreePrev() moves it to the same row
** as it would have been on if the call to BtreeDelete() had been omitted.
**
** The BTREE_IDXDELETE bit of flags indicates that this is a delete of
** an index entry where the corresponding table row has already been deleted.
** The BTREE_IDXDELETE bit is a hint that is not used by this implementation,
** The BTREE_AUXDELETE bit of flags indicates that is one of several deletes
** associated with a single table entry and its indexes.  Only one of those
** deletes is considered the "primary" delete.  The primary delete occurs
** on a cursor that is not a BTREE_FORDELETE cursor.  All but one delete
** operation on non-FORDELETE cursors is tagged with the AUXDELETE flag.
** The BTREE_AUXDELETE bit is a hint that is not used by this implementation,
** but which might be used by alternative storage engines.
*/
int sqlite3BtreeDelete(BtCursor *pCur, u8 flags){
  Btree *p = pCur->pBtree;
  BtShared *pBt = p->pBt;              
  int rc;                              /* Return code */
  MemPage *pPage;                      /* Page to delete cell from */

  assert( pBt->inTransaction==TRANS_WRITE );
  assert( (pBt->btsFlags & BTS_READ_ONLY)==0 );
  assert( pCur->curFlags & BTCF_WriteFlag );
  assert( hasSharedCacheTableLock(p, pCur->pgnoRoot, pCur->pKeyInfo!=0, 2) );
  assert( !hasReadConflicts(p, pCur->pgnoRoot) );
  assert( pCur->aiIdx[pCur->iPage]<pCur->apPage[pCur->iPage]->nCell );
  assert( pCur->eState==CURSOR_VALID );
  assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_IDXDELETE))==0 );
  assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );

  iCellDepth = pCur->iPage;
  iCellIdx = pCur->aiIdx[iCellDepth];
  pPage = pCur->apPage[iCellDepth];
  pCell = findCell(pPage, iCellIdx);

  /* If the page containing the entry to delete is not a leaf page, move

);
int sqlite3BtreeCursorHasMoved(BtCursor*);
int sqlite3BtreeCursorRestore(BtCursor*, int*);
int sqlite3BtreeDelete(BtCursor*, u8 flags);

/* Allowed flags for the 2nd argument to sqlite3BtreeDelete() */
#define BTREE_SAVEPOSITION 0x02  /* Leave cursor pointing at NEXT or PREV */
#define BTREE_IDXDELETE    0x04  /* this is index, table row already deleted */
#define BTREE_AUXDELETE    0x04  /* not the primary delete operation */

int sqlite3BtreeInsert(BtCursor*, const void *pKey, i64 nKey,
                                  const void *pData, int nData,
                                  int nZero, int bias, int seekResult);
int sqlite3BtreeFirst(BtCursor*, int *pRes);
int sqlite3BtreeLast(BtCursor*, int *pRes);
int sqlite3BtreeNext(BtCursor*, int *pRes);

    /* Unless this is a view, open cursors for the table we are 
    ** deleting from and all its indices. If this is a view, then the
    ** only effect this statement has is to fire the INSTEAD OF 
    ** triggers.
    */
    if( !isView ){
      int iAddrOnce = 0;
      u8 p5 = (eOnePass==ONEPASS_OFF ? 0 : OPFLAG_FORDELETE);
      if( eOnePass==ONEPASS_MULTI ){
        iAddrOnce = sqlite3CodeOnce(pParse); VdbeCoverage(v);
      }
      testcase( IsVirtual(pTab) );
      sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, p5, iTabCur, 
                                 aToOpen, &iDataCur, &iIdxCur);
      sqlite3OpenTableAndIndices(pParse, pTab, OP_OpenWrite, OPFLAG_FORDELETE,
                                 iTabCur, aToOpen, &iDataCur, &iIdxCur);
      assert( pPk || IsVirtual(pTab) || iDataCur==iTabCur );
      assert( pPk || IsVirtual(pTab) || iIdxCur==iDataCur+1 );
      if( eOnePass==ONEPASS_MULTI ) sqlite3VdbeJumpHere(v, iAddrOnce);
    }
  
    /* Set up a loop over the rowids/primary-keys that were found in the
    ** where-clause loop above.

  if( pTab->pSelect==0 ){
    u8 p5 = 0;
    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur,0,iIdxNoSeek);
    sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, (count?OPFLAG_NCHANGE:0));
    if( count ){
      sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_TRANSIENT);
    }
    if( eMode!=ONEPASS_OFF ){
      sqlite3VdbeChangeP5(v, OPFLAG_AUXDELETE);
    }
    if( iIdxNoSeek>=0 ){
      sqlite3VdbeAddOp1(v, OP_Delete, iIdxNoSeek);
      if( eMode!=ONEPASS_OFF ) p5 = OPFLAG_IDXDELETE;
    }
    if( eMode==ONEPASS_MULTI ) p5 |= OPFLAG_SAVEPOSITION;
    sqlite3VdbeChangeP5(v, p5);
  }

  /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
  ** handle rows (possibly in other tables) that refer via a foreign key

** If pTab is a virtual table, then this routine is a no-op and the
** *piDataCur and *piIdxCur values are left uninitialized.
*/
int sqlite3OpenTableAndIndices(
  Parse *pParse,   /* Parsing context */
  Table *pTab,     /* Table to be opened */
  int op,          /* OP_OpenRead or OP_OpenWrite */
  u8 p5,           /* P5 value for OP_Open* instructions */
  u8 p5,           /* P5 value for OP_Open* opcodes (except on WITHOUT ROWID) */
  int iBase,       /* Use this for the table cursor, if there is one */
  u8 *aToOpen,     /* If not NULL: boolean for each table and index */
  int *piDataCur,  /* Write the database source cursor number here */
  int *piIdxCur    /* Write the first index cursor number here */
){
  int i;
  int iDb;

  }else{
    sqlite3TableLock(pParse, iDb, pTab->tnum, op==OP_OpenWrite, pTab->zName);
  }
  if( piIdxCur ) *piIdxCur = iBase;
  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    int iIdxCur = iBase++;
    assert( pIdx->pSchema==pTab->pSchema );
    if( IsPrimaryKeyIndex(pIdx) && !HasRowid(pTab) && piDataCur ){
      *piDataCur = iIdxCur;
    }
    if( aToOpen==0 || aToOpen[i+1] ){
      sqlite3VdbeAddOp3(v, op, iIdxCur, pIdx->tnum, iDb);
      sqlite3VdbeSetP4KeyInfo(pParse, pIdx);
      sqlite3VdbeChangeP5(v, p5);
      VdbeComment((v, "%s", pIdx->zName));
    }
    if( IsPrimaryKeyIndex(pIdx) && !HasRowid(pTab) ){
      if( piDataCur ) *piDataCur = iIdxCur;
    }else{
      sqlite3VdbeChangeP5(v, p5);
    }
  }
  if( iBase>pParse->nTab ) pParse->nTab = iBase;
  return i;
}

#define OPFLAG_TYPEOFARG     0x80    /* OP_Column only used for typeof() */
#define OPFLAG_BULKCSR       0x01    /* OP_Open** used to open bulk cursor */
#define OPFLAG_SEEKEQ        0x02    /* OP_Open** cursor uses EQ seek only */
#define OPFLAG_FORDELETE     0x08    /* OP_Open should use BTREE_FORDELETE */
#define OPFLAG_P2ISREG       0x10    /* P2 to OP_Open** is a register number */
#define OPFLAG_PERMUTE       0x01    /* OP_Compare: use the permutation */
#define OPFLAG_SAVEPOSITION  0x02    /* OP_Delete: keep cursor position */
#define OPFLAG_IDXDELETE     0x04    /* OP_Delete: index in a DELETE op */
#define OPFLAG_AUXDELETE     0x04    /* OP_Delete: index in a DELETE op */

/*
 * Each trigger present in the database schema is stored as an instance of
 * struct Trigger. 
 *
 * Pointers to instances of struct Trigger are stored in two ways.
 * 1. In the "trigHash" hash table (part of the sqlite3* that represents the 

  Vdbe *p                    /* The VDBE */
){
  Op *aOp = p->aOp;          /* Copy of p->aOp */
  Op *pOp = aOp;             /* Current operation */
#if defined(SQLITE_DEBUG) || defined(VDBE_PROFILE)
  Op *pOrigOp;               /* Value of pOp at the top of the loop */
#endif
#ifdef SQLITE_DEBUG
  int nExtraDelete = 0;      /* Verifies FORDELETE and AUXDELETE flags */
#endif
  int rc = SQLITE_OK;        /* Value to return */
  sqlite3 *db = p->db;       /* The database */
  u8 resetSchemaOnFault = 0; /* Reset schema after an error if positive */
  u8 encoding = ENC(db);     /* The database encoding */
  int iCompare = 0;          /* Result of last OP_Compare operation */
  unsigned nVmStep = 0;      /* Number of virtual machine steps */
#ifndef SQLITE_OMIT_PROGRESS_CALLBACK

  assert( nField>=0 );
  testcase( nField==0 );  /* Table with INTEGER PRIMARY KEY and nothing else */
  pCur = allocateCursor(p, pOp->p1, nField, iDb, CURTYPE_BTREE);
  if( pCur==0 ) goto no_mem;
  pCur->nullRow = 1;
  pCur->isOrdered = 1;
  pCur->pgnoRoot = p2;
#ifdef SQLITE_DEBUG
  pCur->wrFlag = wrFlag;
#endif
  rc = sqlite3BtreeCursor(pX, p2, wrFlag, pKeyInfo, pCur->uc.pCursor);
  pCur->pKeyInfo = pKeyInfo;
  /* Set the VdbeCursor.isTable variable. Previous versions of
  ** SQLite used to check if the root-page flags were sane at this point
  ** and report database corruption if they were not, but this check has
  ** since moved into the btree layer.  */  
  pCur->isTable = pOp->p4type!=P4_KEYINFO;

** the cursor will be left pointing at  either the next or the previous
** record in the table. If it is left pointing at the next record, then
** the next Next instruction will be a no-op. As a result, in this case
** it is ok to delete a record from within a Next loop. If 
** OPFLAG_SAVEPOSITION bit of P5 is clear, then the cursor will be
** left in an undefined state.
**
** If the OPFLAG_IDXDELETE bit is set on P5, that indicates that this
** delete is on an index cursor where the corresponding table row has
** already been deleted.
** If the OPFLAG_AUXDELETE bit is set on P5, that indicates that this
** delete one of several associated with deleting a table row and all its
** associated index entries.  Exactly one of those deletes is the "primary"
** delete.  The others are all on OPFLAG_FORDELETE cursors or else are
** marked with the AUXDELETE flag.
**
** If the OPFLAG_NCHANGE flag of P2 (NB: P2 not P5) is set, then the row
** change count is incremented (otherwise not).
**
** P1 must not be pseudo-table.  It has to be a real table with
** multiple rows.
**

  ** is being deleted */
  if( pOp->p4.z && pC->isTable && pOp->p5==0 ){
    i64 iKey = 0;
    sqlite3BtreeKeySize(pC->uc.pCursor, &iKey);
    assert( pC->movetoTarget==iKey ); 
  }
#endif
 
  assert( (pOp->p5 & ~(OPFLAG_SAVEPOSITION|OPFLAG_IDXDELETE))==0 );

  /* Only flags that can be set are SAVEPOISTION and AUXDELETE */ 
  assert( (pOp->p5 & ~(OPFLAG_SAVEPOSITION|OPFLAG_AUXDELETE))==0 );
  assert( OPFLAG_SAVEPOSITION==BTREE_SAVEPOSITION );
  assert( OPFLAG_IDXDELETE==BTREE_IDXDELETE );
  assert( OPFLAG_AUXDELETE==BTREE_AUXDELETE );

#ifdef SQLITE_DEBUG
  if( p->pFrame==0 ){
    if( pC->isEphemeral==0
        && (pOp->p5 & OPFLAG_AUXDELETE)==0
        && (pC->wrFlag & OPFLAG_FORDELETE)==0
      ){
      nExtraDelete++;
    }
    if( pOp->p2 & OPFLAG_NCHANGE ){
      nExtraDelete--;
    }
  }
#endif

  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
  pC->cacheStatus = CACHE_STALE;

  /* Invoke the update-hook if required. */
  if( rc==SQLITE_OK && hasUpdateCallback ){
    db->xUpdateCallback(db->pUpdateArg, SQLITE_DELETE,
                        db->aDb[pC->iDb].zName, pOp->p4.z, pC->movetoTarget);

  pCrsr = pC->uc.pCursor;
  assert( pCrsr!=0 );
  assert( pOp->p5==0 );
  r.pKeyInfo = pC->pKeyInfo;
  r.nField = (u16)pOp->p3;
  r.default_rc = 0;
  r.aMem = &aMem[pOp->p2];
#ifdef SQLITE_DEBUG
  { int i; for(i=0; i<r.nField; i++) assert( memIsValid(&r.aMem[i]) ); }
#endif
  rc = sqlite3BtreeMovetoUnpacked(pCrsr, &r, 0, 0, &res);
  if( rc==SQLITE_OK && res==0 ){
    rc = sqlite3BtreeDelete(pCrsr, 0);
    rc = sqlite3BtreeDelete(pCrsr, BTREE_AUXDELETE);
  }
  assert( pC->deferredMoveto==0 );
  pC->cacheStatus = CACHE_STALE;
  break;
}

/* Opcode: IdxRowid P1 P2 * * *

  ** release the mutexes on btrees that were acquired at the
  ** top. */
vdbe_return:
  db->lastRowid = lastRowid;
  testcase( nVmStep>0 );
  p->aCounter[SQLITE_STMTSTATUS_VM_STEP] += (int)nVmStep;
  sqlite3VdbeLeave(p);
  assert( rc!=SQLITE_OK || nExtraDelete==0 
       || sqlite3_strlike("DELETE%",p->zSql,0)!=0 
  );
  return rc;

  /* Jump to here if a string or blob larger than SQLITE_MAX_LENGTH
  ** is encountered.
  */
too_big:
  sqlite3VdbeError(p, "string or blob too big");

  u8 eCurType;          /* One of the CURTYPE_* values above */
  i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */
  u8 nullRow;           /* True if pointing to a row with no data */
  u8 deferredMoveto;    /* A call to sqlite3BtreeMoveto() is needed */
  u8 isTable;           /* True for rowid tables.  False for indexes */
#ifdef SQLITE_DEBUG
  u8 seekOp;            /* Most recent seek operation on this cursor */
  u8 wrFlag;            /* The wrFlag argument to sqlite3BtreeCursor() */
#endif
  Bool isEphemeral:1;   /* True for an ephemeral table */
  Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
  Pgno pgnoRoot;        /* Root page of the open btree cursor */
  i16 nField;           /* Number of fields in the header */
  u16 nHdrParsed;       /* Number of header fields parsed so far */

proc analyze_delete_program {sql} {
  # Build a map from root page to table/index name.
  db eval {
    SELECT name, rootpage FROM sqlite_master
  } {
    set T($rootpage) $name
  }

  # Calculate the results.
  set res [list]
  
  # For each OpenWrite instruction generated for the proposed DELETE
  # statement, add the following array entries:
  #
  #   $M(<cursor number>) -> <object name>
  #   $O(<object name>)   -> "*" | ""
  #
  # The O() entry is set to "*" if the BTREE_FORDELETE flag is specified,
  # or "" otherwise.
  #
  db eval "EXPLAIN $sql" R {
    if {$R(opcode) == "OpenWrite"} {
      set obj $T($R(p2))
      if {"0x$R(p5)" & 0x08} { append obj *}
      lappend res $obj
    }
  }
    if {$R(opcode)=="OpenWrite"} {
      set root $R(p2)
      set csr $R(p1)
      if {[info exists T($root)]} { set M($csr) $T($root) }

      set obj $T($root)
      set O($obj) ""
      if {"0x$R(p5)" & 0x08} { 
        set O($obj) *
      } else {
        set O($obj) ""
      }
    }
  }

  db eval "EXPLAIN $sql" R {
    if {$R(opcode) == "Delete"} {
      set csr $R(p1)
      if {[info exists M($csr)]} {
        set idxdelete [expr {("0x$R(p5)" & 0x04) ? 1 : 0}]
        if {$idxdelete} {
          append O($M($csr)) "+"
        }
      }
    }
  }

  set res [list]
  foreach {k v} [array get O] {
    lappend res "${k}${v}"
  }

  lsort $res
}

proc do_adp_test {tn sql res} {
  uplevel [list do_test $tn [list analyze_delete_program $sql] [list {*}$res]]
}

do_execsql_test 1.0 {
  CREATE TABLE t1(a PRIMARY KEY, b);
}

foreach {tn sql res} {
  1 { DELETE FROM t1 WHERE a=?}          { sqlite_autoindex_t1_1  t1* }
  2 { DELETE FROM t1 WHERE a=? AND b=? } { sqlite_autoindex_t1_1  t1 }
  3 { DELETE FROM t1 WHERE a>? }         { sqlite_autoindex_t1_1  t1* }
  4 { DELETE FROM t1 WHERE rowid=? }     { sqlite_autoindex_t1_1*  t1 }
  1 { DELETE FROM t1 WHERE a=?}          { sqlite_autoindex_t1_1  t1*+ }
  2 { DELETE FROM t1 WHERE a=? AND b=? } { sqlite_autoindex_t1_1  t1+  }
  3 { DELETE FROM t1 WHERE a>? }         { sqlite_autoindex_t1_1  t1*+ }
  4 { DELETE FROM t1 WHERE rowid=? }     { sqlite_autoindex_t1_1*  t1  }
} {
  do_adp_test 1.$tn $sql $res
}

do_execsql_test 2.0 {
  CREATE TABLE t2(a, b, c);
  CREATE INDEX t2a ON t2(a);
  CREATE INDEX t2b ON t2(b);
  CREATE INDEX t2c ON t2(c);
}
foreach {tn sql res} {
  1 { DELETE FROM t2 WHERE a=?}          { t2* t2a t2b* t2c* }
  2 { DELETE FROM t2 WHERE a=? AND +b=?} { t2 t2a t2b* t2c* }
  1 { DELETE FROM t2 WHERE a=?}          { t2*+ t2a t2b* t2c* }
  2 { DELETE FROM t2 WHERE a=? AND +b=?} { t2+ t2a t2b* t2c* }
  3 { DELETE FROM t2 WHERE a=? OR b=?}   { t2 t2a* t2b* t2c* }
  4 { DELETE FROM t2 WHERE +a=? }        { t2 t2a* t2b* t2c* }
  5 { DELETE FROM t2 WHERE rowid=? }     { t2 t2a* t2b* t2c* }
} {
  do_adp_test 2.$tn $sql $res
}

  btree_close_cursor $csr
  db eval { COMMIT }

  db eval {
    SELECT * FROM x2;
  }
} {6 {} {} {}}


#-------------------------------------------------------------------------
#
reset_db 
do_execsql_test 4.0 {
  CREATE TABLE log(x);
  CREATE TABLE p1(one PRIMARY KEY, two);

  CREATE TRIGGER tr_bd BEFORE DELETE ON p1 BEGIN
    INSERT INTO log VALUES('delete');
  END;
  INSERT INTO p1 VALUES('a', 'A'), ('b', 'B'), ('c', 'C');
  DELETE FROM p1 WHERE one = 'a';
}

reset_db
do_execsql_test 4.1 {
  BEGIN TRANSACTION;
  CREATE TABLE tbl(a PRIMARY KEY, b, c);
  CREATE TABLE log(a, b, c);
  INSERT INTO "tbl" VALUES(1,2,3);
  CREATE TRIGGER the_trigger BEFORE DELETE ON tbl BEGIN 
    INSERT INTO log VALUES(1, 2,3);
  END;
  COMMIT;
  DELETE FROM tbl WHERE a=1;
}

reset_db
do_execsql_test 5.1 {
  PRAGMA foreign_keys = 1;
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b);
  CREATE TABLE t2(
      c INTEGER PRIMARY KEY,
      d INTEGER DEFAULT 1 REFERENCES t1 ON DELETE SET DEFAULT
  );
} {}
do_execsql_test 5.2 {
  INSERT INTO t1 VALUES(1, 'one');
  INSERT INTO t1 VALUES(2, 'two');
  INSERT INTO t2 VALUES(1, 2);
  SELECT * FROM t2;
} {1 2}
do_execsql_test 5.3 {
  DELETE FROM t1 WHERE a = 2;
} {}


finish_test