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SQLite training in Houston TX on 2019-11-05 (details)
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Overview
Comment:Correctly handle self-referential foreign keys on WITHOUT ROWID tables.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | omit-rowid
Files: files | file ages | folders
SHA1: af128862ab6008df9dda1ee90f93f9efd629e259
User & Date: drh 2013-11-04 13:56:00
Context
2013-11-04
15:23
Correctly handle changing counting when inserting and deleting on WITHOUT ROWID tables. Add more FOREIGN KEY test cases. check-in: d072bcd0 user: drh tags: omit-rowid
13:56
Correctly handle self-referential foreign keys on WITHOUT ROWID tables. check-in: af128862 user: drh tags: omit-rowid
2013-11-03
02:27
Improved comments on foreign key logic. check-in: 1315d910 user: drh tags: omit-rowid
Changes
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Changes to src/fkey.c.

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    sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
  }

  sqlite3VdbeResolveLabel(v, iOk);
  sqlite3VdbeAddOp1(v, OP_Close, iCur);
}

























































/*
** This function is called to generate code executed when a row is deleted
** from the parent table of foreign key constraint pFKey and, if pFKey is 
** deferred, when a row is inserted into the same table. When generating
** code for an SQL UPDATE operation, this function may be called twice -
** once to "delete" the old row and once to "insert" the new row.
**
................................................................................
  for(i=0; i<pFKey->nCol; i++){
    Expr *pLeft;                  /* Value from parent table row */
    Expr *pRight;                 /* Column ref to child table */
    Expr *pEq;                    /* Expression (pLeft = pRight) */
    i16 iCol;                     /* Index of column in child table */ 
    const char *zCol;             /* Name of column in child table */

    pLeft = sqlite3Expr(db, TK_REGISTER, 0);
    if( pLeft ){
      /* Set the collation sequence and affinity of the LHS of each TK_EQ
      ** expression to the parent key column defaults.  */
      if( pIdx ){
        Column *pCol;
        const char *zColl;
        iCol = pIdx->aiColumn[i];
        pCol = &pTab->aCol[iCol];
        if( pTab->iPKey==iCol ) iCol = -1;
        pLeft->iTable = regData+iCol+1;
        pLeft->affinity = pCol->affinity;
        zColl = pCol->zColl;
        if( zColl==0 ) zColl = db->pDfltColl->zName;
        pLeft = sqlite3ExprAddCollateString(pParse, pLeft, zColl);
      }else{
        pLeft->iTable = regData;
        pLeft->affinity = SQLITE_AFF_INTEGER;
      }
    }

    iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
    assert( iCol>=0 );
    zCol = pFKey->pFrom->aCol[iCol].zName;
    pRight = sqlite3Expr(db, TK_ID, zCol);
    pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
    pWhere = sqlite3ExprAnd(db, pWhere, pEq);
  }

  /* If the child table is the same as the parent table, and this scan
  ** is taking place as part of a DELETE operation (operation D.2), omit the
  ** row being deleted from the scan by adding ($rowid != rowid) to the WHERE 
  ** clause, where $rowid is the rowid of the row being deleted.  */







  if( pTab==pFKey->pFrom && nIncr>0 && HasRowid(pTab) /*FIXME*/ ){
    Expr *pNe;                    /* Expression (pLeft != pRight) */
    Expr *pLeft;                  /* Value from parent table row */
    Expr *pRight;                 /* Column ref to child table */
    pLeft = sqlite3Expr(db, TK_REGISTER, 0);
    pRight = sqlite3Expr(db, TK_COLUMN, 0);
    if( pLeft && pRight ){
      pLeft->iTable = regData;
      pLeft->affinity = SQLITE_AFF_INTEGER;


      pRight->iTable = pSrc->a[0].iCursor;
      pRight->iColumn = -1;











    }
    pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);

    pWhere = sqlite3ExprAnd(db, pWhere, pNe);
  }

  /* Resolve the references in the WHERE clause. */
  memset(&sNameContext, 0, sizeof(NameContext));
  sNameContext.pSrcList = pSrc;
  sNameContext.pParse = pParse;







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    sqlite3VdbeAddOp2(v, OP_FkCounter, pFKey->isDeferred, nIncr);
  }

  sqlite3VdbeResolveLabel(v, iOk);
  sqlite3VdbeAddOp1(v, OP_Close, iCur);
}


/*
** Return an Expr object that refers to a memory register corresponding
** to column iCol of table pTab.
**
** regBase is the first of an array of register that contains the data
** for pTab.  regBase itself holds the rowid.  regBase+1 holds the first
** column.  regBase+2 holds the second column, and so forth.
*/
static Expr *exprTableRegister(
  Parse *pParse,     /* Parsing and code generating context */
  Table *pTab,       /* The table whose content is at r[regBase]... */
  int regBase,       /* Contents of table pTab */
  i16 iCol           /* Which column of pTab is desired */
){
  Expr *pExpr;
  Column *pCol;
  const char *zColl;
  sqlite3 *db = pParse->db;

  pExpr = sqlite3Expr(db, TK_REGISTER, 0);
  if( pExpr ){
    if( iCol>=0 && iCol!=pTab->iPKey ){
      pCol = &pTab->aCol[iCol];
      pExpr->iTable = regBase + iCol + 1;
      pExpr->affinity = pCol->affinity;
      zColl = pCol->zColl;
      if( zColl==0 ) zColl = db->pDfltColl->zName;
      pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl);
    }else{
      pExpr->iTable = regBase;
      pExpr->affinity = SQLITE_AFF_INTEGER;
    }
  }
  return pExpr;
}

/*
** Return an Expr object that refers to column iCol of table pTab which
** has cursor iCur.
*/
static Expr *exprTableColumn(
  sqlite3 *db,      /* The database connection */
  Table *pTab,      /* The table whose column is desired */
  int iCursor,      /* The open cursor on the table */
  i16 iCol          /* The column that is wanted */
){
  Expr *pExpr = sqlite3Expr(db, TK_COLUMN, 0);
  if( pExpr ){
    pExpr->pTab = pTab;
    pExpr->iTable = iCursor;
    pExpr->iColumn = iCol;
  }
  return pExpr;
}

/*
** This function is called to generate code executed when a row is deleted
** from the parent table of foreign key constraint pFKey and, if pFKey is 
** deferred, when a row is inserted into the same table. When generating
** code for an SQL UPDATE operation, this function may be called twice -
** once to "delete" the old row and once to "insert" the new row.
**
................................................................................
  for(i=0; i<pFKey->nCol; i++){
    Expr *pLeft;                  /* Value from parent table row */
    Expr *pRight;                 /* Column ref to child table */
    Expr *pEq;                    /* Expression (pLeft = pRight) */
    i16 iCol;                     /* Index of column in child table */ 
    const char *zCol;             /* Name of column in child table */








    iCol = pIdx ? pIdx->aiColumn[i] : -1;












    pLeft = exprTableRegister(pParse, pTab, regData, iCol);
    iCol = aiCol ? aiCol[i] : pFKey->aCol[0].iFrom;
    assert( iCol>=0 );
    zCol = pFKey->pFrom->aCol[iCol].zName;
    pRight = sqlite3Expr(db, TK_ID, zCol);
    pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
    pWhere = sqlite3ExprAnd(db, pWhere, pEq);
  }

  /* If the child table is the same as the parent table, then add terms
  ** to the WHERE clause that prevent this entry from being scanned.
  ** The added WHERE clause terms are like this:
  **
  **     $current_rowid!=rowid
  **     NOT( $current_a==a AND $current_b==b AND ... )
  **
  ** The first form is used for rowid tables.  The second form is used
  ** for WITHOUT ROWID tables.  In the second form, the primary key is
  ** (a,b,...)
  */
  if( pTab==pFKey->pFrom && nIncr>0 ){
    Expr *pNe;                    /* Expression (pLeft != pRight) */
    Expr *pLeft;                  /* Value from parent table row */
    Expr *pRight;                 /* Column ref to child table */





    if( HasRowid(pTab) ){
      pLeft = exprTableRegister(pParse, pTab, regData, -1);
      pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, -1);

      pNe = sqlite3PExpr(pParse, TK_NE, pLeft, pRight, 0);
    }else{
      int i;
      Expr *pEq, *pAll = 0;
      Index *pPk = sqlite3PrimaryKeyIndex(pTab);
      for(i=0; i<pPk->nKeyCol; i++){
        i16 iCol = pIdx->aiColumn[i];
        pLeft = exprTableRegister(pParse, pTab, regData, iCol);
        pRight = exprTableColumn(db, pTab, pSrc->a[0].iCursor, iCol);
        pEq = sqlite3PExpr(pParse, TK_EQ, pLeft, pRight, 0);
        pAll = sqlite3ExprAnd(db, pAll, pEq);
      }
      pNe = sqlite3PExpr(pParse, TK_NOT, pAll, 0, 0);
    }
    pWhere = sqlite3ExprAnd(db, pWhere, pNe);
  }

  /* Resolve the references in the WHERE clause. */
  memset(&sNameContext, 0, sizeof(NameContext));
  sNameContext.pSrcList = pSrc;
  sNameContext.pParse = pParse;