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Overview
Comment:An optimization that converts "a IN (b)" into "a==b". Seems to work, but needs additional test cases.
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Timelines: family | ancestors | degenerate_IN
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SHA1: 8b4c3c5e506267c18550063cb9bd93519c871b0e
User & Date: drh 2012-10-16 21:08:03
Context
2012-10-16
21:08
An optimization that converts "a IN (b)" into "a==b". Seems to work, but needs additional test cases. Leaf check-in: 8b4c3c5e user: drh tags: degenerate_IN
2012-10-15
20:28
Correct comments and enhance readability of the mkvsix tool. check-in: 2c3af657 user: mistachkin tags: trunk
Changes
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Changes to src/parse.y.

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  A.zEnd = Y.zEnd;
}
%ifndef SQLITE_OMIT_SUBQUERY
  %type in_op {int}
  in_op(A) ::= IN.      {A = 0;}
  in_op(A) ::= NOT IN.  {A = 1;}
  expr(A) ::= expr(X) in_op(N) LP exprlist(Y) RP(E). [IN] {


    if( Y==0 ){
      /* Expressions of the form
      **
      **      expr1 IN ()
      **      expr1 NOT IN ()
      **
      ** simplify to constants 0 (false) and 1 (true), respectively,
      ** regardless of the value of expr1.
      */
      A.pExpr = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &sqlite3IntTokens[N]);
      sqlite3ExprDelete(pParse->db, X.pExpr);










    }else{
      A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
      if( A.pExpr ){
        A.pExpr->x.pList = Y;
        sqlite3ExprSetHeight(pParse, A.pExpr);
      }else{
        sqlite3ExprListDelete(pParse->db, Y);
      }
      if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
    }
    A.zStart = X.zStart;
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= LP(B) select(X) RP(E). {







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  A.zEnd = Y.zEnd;
}
%ifndef SQLITE_OMIT_SUBQUERY
  %type in_op {int}
  in_op(A) ::= IN.      {A = 0;}
  in_op(A) ::= NOT IN.  {A = 1;}
  expr(A) ::= expr(X) in_op(N) LP exprlist(Y) RP(E). [IN] {
    sqlite3 *db = pParse->db;
    ExprList *pY = Y;
    if( pY==0 ){
      /* Expressions of the form
      **
      **      expr1 IN ()
      **      expr1 NOT IN ()
      **
      ** simplify to constants 0 (false) and 1 (true), respectively,
      ** regardless of the value of expr1.
      */
      A.pExpr = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &sqlite3IntTokens[N]);
      sqlite3ExprDelete(db, X.pExpr);
    }else if( pY->nExpr==1 ){
      /* If the RHS of the IN operator has a single term, simplify as follows:
      **
      **      expr1 IN (Y)        -->      expr1 = Y
      **      expr1 NOT IN (Y)    -->      expr1 <> Y
      */
      assert( TK_EQ==TK_NE+1 );
      A.pExpr = sqlite3PExpr(pParse, TK_EQ-N, X.pExpr, pY->a[0].pExpr, 0);
      pY->a[0].pExpr = 0;
      sqlite3ExprListDelete(db, pY);
    }else{
      A.pExpr = sqlite3PExpr(pParse, TK_IN, X.pExpr, 0, 0);
      if( A.pExpr ){
        A.pExpr->x.pList = pY;
        sqlite3ExprSetHeight(pParse, A.pExpr);
      }else{
        sqlite3ExprListDelete(pParse->db, pY);
      }
      if( N ) A.pExpr = sqlite3PExpr(pParse, TK_NOT, A.pExpr, 0, 0);
    }
    A.zStart = X.zStart;
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= LP(B) select(X) RP(E). {