SQLite

**    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
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.271 2005/09/19 17:35:53 drh Exp $
** $Id: select.c,v 1.272 2005/09/19 21:05:49 drh Exp $
*/
#include "sqliteInt.h"


/*
** Allocate a new Select structure and return a pointer to that
** structure.

*/
static void addWhereTerm(
  const char *zCol,        /* Name of the column */
  const Table *pTab1,      /* First table */
  const char *zAlias1,     /* Alias for first table.  May be NULL */
  const Table *pTab2,      /* Second table */
  const char *zAlias2,     /* Alias for second table.  May be NULL */
  int iRightJoinTable,     /* VDBE cursor for the right table */
  Expr **ppExpr            /* Add the equality term to this expression */
){
  Expr *pE1a, *pE1b, *pE1c;
  Expr *pE2a, *pE2b, *pE2c;
  Expr *pE;

  pE1a = createIdExpr(zCol);
  pE2a = createIdExpr(zCol);
  if( zAlias1==0 ){
    zAlias1 = pTab1->zName;
  }
  pE1b = createIdExpr(zAlias1);
  if( zAlias2==0 ){
    zAlias2 = pTab2->zName;
  }
  pE2b = createIdExpr(zAlias2);
  pE1c = sqlite3Expr(TK_DOT, pE1b, pE1a, 0);
  pE2c = sqlite3Expr(TK_DOT, pE2b, pE2a, 0);
  pE = sqlite3Expr(TK_EQ, pE1c, pE2c, 0);
  ExprSetProperty(pE, EP_FromJoin);
  pE->iRightJoinTable = iRightJoinTable;
  *ppExpr = sqlite3ExprAnd(*ppExpr, pE);
}

/*
** Set the EP_FromJoin property on all terms of the given expression.
** And set the Expr.iRightJoinTable to iTable for every term in the
** expression.
**
** The EP_FromJoin property is used on terms of an expression to tell
** the LEFT OUTER JOIN processing logic that this term is part of the
** join restriction specified in the ON or USING clause and not a part
** of the more general WHERE clause.  These terms are moved over to the
** WHERE clause during join processing but we need to remember that they
** originated in the ON or USING clause.
**
** The Expr.iRightJoinTable tells the WHERE clause processing that the
** expression depends on table iRightJoinTable even if that table is not
** explicitly mentioned in the expression.  That information is needed
** for cases like this:
**
**    SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.b AND t1.x=5
**
** The where clause needs to defer the handling of the t1.x=5
** term until after the t2 loop of the join.  In that way, a
** NULL t2 row will be inserted whenever t1.x!=5.  If we do not
** defer the handling of t1.x=5, it will be processed immediately
** after the t1 loop and rows with t1.x!=5 will never appear in
** the output, which is incorrect.
*/
static void setJoinExpr(Expr *p){
static void setJoinExpr(Expr *p, int iTable){
  while( p ){
    ExprSetProperty(p, EP_FromJoin);
    p->iRightJoinTable = iTable;
    setJoinExpr(p->pLeft);
    setJoinExpr(p->pLeft, iTable);
    p = p->pRight;
  } 
}

/*
** This routine processes the join information for a SELECT statement.
** ON and USING clauses are converted into extra terms of the WHERE clause.

           "an ON or USING clause", 0);
        return 1;
      }
      for(j=0; j<pLeftTab->nCol; j++){
        char *zName = pLeftTab->aCol[j].zName;
        if( columnIndex(pRightTab, zName)>=0 ){
          addWhereTerm(zName, pLeftTab, pLeft->zAlias, 
                              pRightTab, pRight->zAlias, &p->pWhere);
                              pRightTab, pRight->zAlias,
                              pRight->iCursor, &p->pWhere);
          
        }
      }
    }

    /* Disallow both ON and USING clauses in the same join
    */
    if( pLeft->pOn && pLeft->pUsing ){
      sqlite3ErrorMsg(pParse, "cannot have both ON and USING "
        "clauses in the same join");
      return 1;
    }

    /* Add the ON clause to the end of the WHERE clause, connected by
    ** an AND operator.
    */
    if( pLeft->pOn ){
      setJoinExpr(pLeft->pOn);
      setJoinExpr(pLeft->pOn, pRight->iCursor);
      p->pWhere = sqlite3ExprAnd(p->pWhere, pLeft->pOn);
      pLeft->pOn = 0;
    }

    /* Create extra terms on the WHERE clause for each column named
    ** in the USING clause.  Example: If the two tables to be joined are 
    ** A and B and the USING clause names X, Y, and Z, then add this

        char *zName = pList->a[j].zName;
        if( columnIndex(pLeftTab, zName)<0 || columnIndex(pRightTab, zName)<0 ){
          sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
            "not present in both tables", zName);
          return 1;
        }
        addWhereTerm(zName, pLeftTab, pLeft->zAlias, 
                            pRightTab, pRight->zAlias, &p->pWhere);
                            pRightTab, pRight->zAlias,
                            pRight->iCursor, &p->pWhere);
      }
    }
  }
  return 0;
}

/*

/*
** 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.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.420 2005/09/19 17:35:53 drh Exp $
** @(#) $Id: sqliteInt.h,v 1.421 2005/09/19 21:05:49 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** Many people are failing to set -DNDEBUG=1 when compiling SQLite.
** Setting NDEBUG makes the code smaller and run faster.  So the following

                         ** or in "<expr> IN (<expr-list)" */
  Token token;           /* An operand token */
  Token span;            /* Complete text of the expression */
  int iTable, iColumn;   /* When op==TK_COLUMN, then this expr node means the
                         ** iColumn-th field of the iTable-th table. */
  AggInfo *pAggInfo;     /* Used by TK_AGG_COLUMN and TK_AGG_FUNCTION */
  int iAgg;              /* Which entry in pAggInfo->aCol[] or ->aFunc[] */
  int iRightJoinTable;   /* If EP_FromJoin, the right table of the join */
  Select *pSelect;       /* When the expression is a sub-select.  Also the
                         ** right side of "<expr> IN (<select>)" */
  Table *pTab;           /* Table for OP_Column expressions. */
};

/*
** The following are the meanings of bits in the Expr.flags field.

** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  This module is reponsible for
** generating the code that loops through a table looking for applicable
** rows.  Indices are selected and used to speed the search when doing
** so is applicable.  Because this module is responsible for selecting
** indices, you might also think of this module as the "query optimizer".
**
** $Id: where.c,v 1.176 2005/09/19 13:15:23 drh Exp $
** $Id: where.c,v 1.177 2005/09/19 21:05:49 drh Exp $
*/
#include "sqliteInt.h"

/*
** The number of bits in a Bitmask.  "BMS" means "BitMask Size".
*/
#define BMS  (sizeof(Bitmask)*8)

  if( pExpr->op==TK_IN ){
    assert( pExpr->pRight==0 );
    pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->pList)
                          | exprSelectTableUsage(pMaskSet, pExpr->pSelect);
  }else{
    pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
  }
  prereqAll = exprTableUsage(pMaskSet, pExpr);
  if( ExprHasProperty(pExpr, EP_FromJoin) ){
    prereqAll |= getMask(pMaskSet, pExpr->iRightJoinTable);
  }
  pTerm->prereqAll = prereqAll = exprTableUsage(pMaskSet, pExpr);
  pTerm->prereqAll = prereqAll;
  pTerm->leftCursor = -1;
  pTerm->iParent = -1;
  pTerm->operator = 0;
  if( allowedOp(pExpr->op) && (pTerm->prereqRight & prereqLeft)==0 ){
    Expr *pLeft = pExpr->pLeft;
    Expr *pRight = pExpr->pRight;
    assert( prereqAll == (pTerm->prereqRight | prereqLeft) ); /* ticket 1433 */
    if( pLeft->op==TK_COLUMN ){
      pTerm->leftCursor = pLeft->iTable;
      pTerm->leftColumn = pLeft->iColumn;
      pTerm->operator = operatorMask(pExpr->op);
    }
    if( pRight && pRight->op==TK_COLUMN ){
      WhereTerm *pNew;

# 2005 September 19
#
# 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 implements regression tests for SQLite library.
#
# This file implements tests for left outer joins containing ON
# clauses that restrict the scope of the left term of the join.
#
# $Id: join5.test,v 1.1 2005/09/19 21:05:50 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl


do_test join5-1.1 {
  execsql {
    BEGIN;
    CREATE TABLE t1(a integer primary key, b integer, c integer);
    CREATE TABLE t2(x integer primary key, y);
    CREATE TABLE t3(p integer primary key, q);
    INSERT INTO t3 VALUES(11,'t3-11');
    INSERT INTO t3 VALUES(12,'t3-12');
    INSERT INTO t2 VALUES(11,'t2-11');
    INSERT INTO t2 VALUES(12,'t2-12');
    INSERT INTO t1 VALUES(1, 5, 0);
    INSERT INTO t1 VALUES(2, 11, 2);
    INSERT INTO t1 VALUES(3, 12, 1);
    COMMIT;
  }
} {}
do_test join5-1.2 {
  execsql {
    select * from t1 left join t2 on t1.b=t2.x and t1.c=1
  }
} {1 5 0 {} {} 2 11 2 {} {} 3 12 1 12 t2-12}
do_test join5-1.3 {
  execsql {
    select * from t1 left join t2 on t1.b=t2.x where t1.c=1
  }
} {3 12 1 12 t2-12}
do_test join5-1.4 {
  execsql {
    select * from t1 left join t2 on t1.b=t2.x and t1.c=1
                     left join t3 on t1.b=t3.p and t1.c=2
  }
} {1 5 0 {} {} {} {} 2 11 2 {} {} 11 t3-11 3 12 1 12 t2-12 {} {}}
do_test join5-1.5 {
  execsql {
    select * from t1 left join t2 on t1.b=t2.x and t1.c=1
                     left join t3 on t1.b=t3.p where t1.c=2
  }
} {2 11 2 {} {} 11 t3-11}


finish_test