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Overview
Comment:Add the IS DISTINCT FROM and IS NOT DISTINCT FROM operators.
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SHA1: 0be4478209fc3544152874fde2750ce86b410221
User & Date: drh 2015-06-13 11:48:52
Context
2015-06-13
19:05
Added test cases based on Bruce Momjian's talk on SQL NULLs. Leaf check-in: 68c168b5 user: drh tags: is-distinct-from
11:48
Add the IS DISTINCT FROM and IS NOT DISTINCT FROM operators. check-in: 0be44782 user: drh tags: is-distinct-from
11:19
Omit mutex calls in pcache1 when the mutex is NULL, for a significant performance improvement. check-in: caf8f574 user: drh tags: trunk
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Changes to src/parse.y.

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      pA->pRight = 0;
    }
  }
}

//    expr1 IS expr2
//    expr1 IS NOT expr2


//
// If expr2 is NULL then code as TK_ISNULL or TK_NOTNULL.  If expr2
// is any other expression, code as TK_IS or TK_ISNOT.
// 
expr(A) ::= expr(X) IS expr(Y).     {
  spanBinaryExpr(&A,pParse,TK_IS,&X,&Y);
  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_ISNULL);
}
expr(A) ::= expr(X) IS NOT expr(Y). {
  spanBinaryExpr(&A,pParse,TK_ISNOT,&X,&Y);
  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_NOTNULL);
}









%include {
  /* Construct an expression node for a unary prefix operator
  */
  static void spanUnaryPrefix(
    ExprSpan *pOut,        /* Write the new expression node here */
    Parse *pParse,         /* Parsing context to record errors */







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      pA->pRight = 0;
    }
  }
}

//    expr1 IS expr2
//    expr1 IS NOT expr2
//    expr1 IS DISTINCT FROM expr2
//    expr1 IS NOT DISTINCT FROM expr2
//
// If expr2 is NULL then code as TK_ISNULL or TK_NOTNULL.  If expr2
// is any other expression, code as TK_IS or TK_ISNOT.
// 
expr(A) ::= expr(X) IS expr(Y).     {
  spanBinaryExpr(&A,pParse,TK_IS,&X,&Y);
  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_ISNULL);
}
expr(A) ::= expr(X) IS NOT expr(Y). {
  spanBinaryExpr(&A,pParse,TK_ISNOT,&X,&Y);
  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_NOTNULL);
}
expr(A) ::= expr(X) IS DISTINCT FROM expr(Y).     {
  spanBinaryExpr(&A,pParse,TK_ISNOT,&X,&Y);
  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_NOTNULL);
}
expr(A) ::= expr(X) IS NOT DISTINCT FROM expr(Y). {
  spanBinaryExpr(&A,pParse,TK_IS,&X,&Y);
  binaryToUnaryIfNull(pParse, Y.pExpr, A.pExpr, TK_ISNULL);
}

%include {
  /* Construct an expression node for a unary prefix operator
  */
  static void spanUnaryPrefix(
    ExprSpan *pOut,        /* Write the new expression node here */
    Parse *pParse,         /* Parsing context to record errors */