SQLite

** Mark term iChild as being a child of term iParent
*/
static void markTermAsChild(WhereClause *pWC, int iChild, int iParent){
  pWC->a[iChild].iParent = iParent;
  pWC->a[iChild].truthProb = pWC->a[iParent].truthProb;
  pWC->a[iParent].nChild++;
}

/*
** Return the N-th AND-connected subterm of pTerm.  Or if pTerm is not
** a conjunction, then return just pTerm when N==0.  If N is exceeds
** the number of available subterms, return NULL.
*/
static WhereTerm *whereNthSubterm(WhereTerm *pTerm, int N){
  if( pTerm->eOperator!=WO_AND ){
    return N==0 ? pTerm : 0;
  }
  if( N<pTerm->u.pAndInfo->wc.nTerm ){
    return &pTerm->u.pAndInfo->wc.a[N];
  }
  return 0;
}

/*
** Subterms pOne and pTwo are contained within WHERE clause pWC.  The
** two subterms are in disjunction - they are OR-ed together.
**
** If these two terms are both of the form:  "A op B" with the same
** A and B values but different operators and if the operators are
** compatible (if one is = and the other is <, for example) then
** add a new virtual AND term to pWC that is the combination of the
** two.
**
** Some examples:
**
**    x<y OR x=y    -->     x<=y
**    x=y OR x=y    -->     x=y
**    x<=y OR x<y   -->     x<=y
**
** The following is NOT generated:
**
**    x<y OR x>y    -->     x!=y     
*/
static void whereCombineDisjuncts(
  SrcList *pSrc,         /* the FROM clause */
  WhereClause *pWC,      /* The complete WHERE clause */
  WhereTerm *pOne,       /* First disjunct */
  WhereTerm *pTwo        /* Second disjunct */
){
  u16 eOp = pOne->eOperator | pTwo->eOperator;
  sqlite3 *db;           /* Database connection (for malloc) */
  Expr *pNew;            /* New virtual expression */
  int op;                /* Operator for the combined expression */
  int idxNew;            /* Index in pWC of the next virtual term */

  if( (pOne->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
  if( (pTwo->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE))==0 ) return;
  if( (eOp & (WO_EQ|WO_LT|WO_LE))!=eOp
   && (eOp & (WO_EQ|WO_GT|WO_GE))!=eOp ) return;
  assert( pOne->pExpr->pLeft!=0 && pOne->pExpr->pRight!=0 );
  assert( pTwo->pExpr->pLeft!=0 && pTwo->pExpr->pRight!=0 );
  if( sqlite3ExprCompare(pOne->pExpr->pLeft, pTwo->pExpr->pLeft, -1) ) return;
  if( sqlite3ExprCompare(pOne->pExpr->pRight, pTwo->pExpr->pRight, -1) )return;
  /* If we reach this point, it means the two subterms can be combined */
  if( (eOp & (eOp-1))!=0 ){
    if( eOp & (WO_LT|WO_LE) ){
      eOp = WO_LE;
    }else{
      assert( eOp & (WO_GT|WO_GE) );
      eOp = WO_GE;
    }
  }
  db = pWC->pWInfo->pParse->db;
  pNew = sqlite3ExprDup(db, pOne->pExpr, 0);
  if( pNew==0 ) return;
  for(op=TK_EQ; eOp!=(WO_EQ<<(op-TK_EQ)); op++){ assert( op<TK_GE ); }
  pNew->op = op;
  idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
  exprAnalyze(pSrc, pWC, idxNew);
}

#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
/*
** Analyze a term that consists of two or more OR-connected
** subterms.  So in:
**
**     ... WHERE  (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)

** Examples of terms under analysis:
**
**     (A)     t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
**     (B)     x=expr1 OR expr2=x OR x=expr3
**     (C)     t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
**     (D)     x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
**     (E)     (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
**     (F)     x>A OR (x=A AND y>=B)
**
** CASE 1:
**
** If all subterms are of the form T.C=expr for some single column of C and
** a single table T (as shown in example B above) then create a new virtual
** term that is an equivalent IN expression.  In other words, if the term
** being analyzed is:
**
**      x = expr1  OR  expr2 = x  OR  x = expr3
**
** then create a new virtual term like this:
**
**      x IN (expr1,expr2,expr3)
**
** CASE 2:
**
** If there are exactly two disjuncts one side has x>A and the other side
** has x=A (for the same x and A) then add a new virtual conjunct term to the
** WHERE clause of the form "x>=A".  Example:
**
**      x>A OR (x=A AND y>B)    adds:    x>=A
**
** The added conjunct can sometimes be helpful in query planning.
**
** CASE 3:
**
** If all subterms are indexable by a single table T, then set
**
**     WhereTerm.eOperator              =  WO_OR
**     WhereTerm.u.pOrInfo->indexable  |=  the cursor number for table T
**
** A subterm is "indexable" if it is of the form

      }else{
        chngToIN &= b;
      }
    }
  }

  /*
  ** Record the set of tables that satisfy case 3.  The set might be
  ** empty.
  */
  pOrInfo->indexable = indexable;
  pTerm->eOperator = indexable==0 ? 0 : WO_OR;

  /* For a two-way OR, attempt to implementation case 2.
  */
  if( indexable && pOrWc->nTerm==2 ){
    int iOne = 0;
    WhereTerm *pOne;
    while( (pOne = whereNthSubterm(&pOrWc->a[0],iOne++))!=0 ){
      int iTwo = 0;
      WhereTerm *pTwo;
      while( (pTwo = whereNthSubterm(&pOrWc->a[1],iTwo++))!=0 ){
        whereCombineDisjuncts(pSrc, pWC, pOne, pTwo);
      }
    }
  }

  /*
  ** chngToIN holds a set of tables that *might* satisfy case 1.  But
  ** we have to do some additional checking to see if case 1 really
  ** is satisfied.
  **
  ** chngToIN will hold either 0, 1, or 2 bits.  The 0-bit case means

        testcase( idxNew==0 );
        exprAnalyze(pSrc, pWC, idxNew);
        pTerm = &pWC->a[idxTerm];
        markTermAsChild(pWC, idxNew, idxTerm);
      }else{
        sqlite3ExprListDelete(db, pList);
      }
      pTerm->eOperator = WO_NOOP;  /* case 1 trumps case 3 */
    }
  }
}
#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */

/*
** The input to this routine is an WhereTerm structure with only the

# 2015-03-16
#
# 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.  The
# focus of this file is testing OR expressions where terms can be
# factored from either side of the OR and combined into a single new
# AND term that is beneficial to the search.  Examples:
#
#      (x>A OR x=A)              -->    ... AND (x>=A)
#      (x>A OR (x=A AND y>=B)    -->    ... AND (x>=A)
#



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

do_execsql_test 1.1 {
  CREATE TABLE t1(a,b,c);
  WITH RECURSIVE c(x) AS (VALUES(0) UNION ALL SELECT x+1 FROM c WHERE x<99)
    INSERT INTO t1(a,b,c) SELECT x, x/10, x%10 FROM c;
  CREATE INDEX t1bc ON t1(b,c);
  SELECT a FROM t1 WHERE b>9 OR b=9 ORDER BY +a;
} {90 91 92 93 94 95 96 97 98 99}
do_execsql_test 1.1eqp {
  EXPLAIN QUERY PLAN
  SELECT a FROM t1 WHERE b>9 OR b=9 ORDER BY +a;
} {/SEARCH TABLE t1 USING INDEX t1bc/}

do_execsql_test 1.2 {
  SELECT a FROM t1 WHERE b>8 OR (b=8 AND c>7) ORDER BY +a;
} {88 89 90 91 92 93 94 95 96 97 98 99}
do_execsql_test 1.2eqp {
  EXPLAIN QUERY PLAN
  SELECT a FROM t1 WHERE b>8 OR (b=8 AND c>7) ORDER BY +a;
} {/SEARCH TABLE t1 USING INDEX t1bc/}

do_execsql_test 1.3 {
  SELECT a FROM t1 WHERE (b=8 AND c>7) OR b>8 ORDER BY +a;
} {88 89 90 91 92 93 94 95 96 97 98 99}
do_execsql_test 1.3eqp {
  EXPLAIN QUERY PLAN
  SELECT a FROM t1 WHERE (b=8 AND c>7) OR b>8 ORDER BY +a;
} {/SEARCH TABLE t1 USING INDEX t1bc/}

do_execsql_test 1.4 {
  SELECT a FROM t1 WHERE (b=8 AND c>7) OR 8<b ORDER BY +a;
} {88 89 90 91 92 93 94 95 96 97 98 99}
do_execsql_test 1.4eqp {
  EXPLAIN QUERY PLAN
  SELECT a FROM t1 WHERE (b=8 AND c>7) OR 8<b ORDER BY +a;
} {/SEARCH TABLE t1 USING INDEX t1bc/}

do_execsql_test 1.5 {
  SELECT a FROM t1 WHERE (b=8 AND c>7) OR (b>8 AND c NOT IN (4,5,6))
   ORDER BY +a;
} {88 89 90 91 92 93 97 98 99}
do_execsql_test 1.5eqp {
  EXPLAIN QUERY PLAN
  SELECT a FROM t1 WHERE (b=8 AND c>7) OR (b>8 AND c NOT IN (4,5,6))
   ORDER BY +a;
} {/SEARCH TABLE t1 USING INDEX t1bc/}

finish_test