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Implement the IS DISTINCT FROM operator per SQL99.

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Reused the Expr node to hold DISTINCT which strongly resembles
 the existing OP info. Define DISTINCT_EXPR which strongly resembles
 the existing OPER_EXPR opType, but with handling for NULLs required
 by SQL99.
We have explicit support for single-element DISTINCT comparisons
 all the way through to the executor. But, multi-element DISTINCTs
 are handled by expanding into a comparison tree in gram.y as is done for
 other row comparisons. Per discussions, it might be desirable to move
 this into one or more purpose-built nodes to be handled in the backend.
Define the optional ROW keyword and token per SQL99.
 This allows single-element row constructs, which were formerly disallowed
 due to shift/reduce conflicts with parenthesized a_expr clauses.
Define the SQL99 TREAT() function. Currently, use as a synonym for CAST().
This commit is contained in:
Thomas G. Lockhart
2002-07-04 15:24:11 +00:00
parent c7eea66c39
commit 68d9fbeb55
10 changed files with 438 additions and 100 deletions
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13
src/backend/parser/parse_expr.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.119 2002/06/20 20:29:32 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.120 2002/07/04 15:24:01 thomas Exp $
*
*-------------------------------------------------------------------------
*/
@ -271,6 +271,17 @@ transformExpr(ParseState *pstate, Node *expr)
result = (Node *) expr;
}
break;
case DISTINCT:
{
Node *lexpr = transformExpr(pstate,
a->lexpr);
Node *rexpr = transformExpr(pstate,
a->rexpr);
result = (Node *) make_op(a->name,
lexpr,
rexpr);
((Expr *)result)->opType = DISTINCT_EXPR;
}
}
break;
}