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Reimplement CASE val WHEN compval1 THEN ... WHEN compval2 THEN ... END

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so that the 'val' is computed only once, per recent discussion.  The
speedup is not much when 'val' is just a simple variable, but could be
significant for larger expressions.  More importantly this avoids issues
with multiple evaluations of a volatile 'val', and it allows the CASE
expression to be reverse-listed in its original form by ruleutils.c.
This commit is contained in:
Tom Lane
2004-03-17 20:48:43 +00:00
parent 8c702ea7ac
commit 55f7c3300d
16 changed files with 248 additions and 55 deletions
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23
src/backend/utils/adt/ruleutils.c
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@ -3,7 +3,7 @@
* back to source text
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.162 2004/01/31 05:09:40 neilc Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.163 2004/03/17 20:48:42 tgl Exp $
*
* This software is copyrighted by Jan Wieck - Hamburg.
*
@ -2564,7 +2564,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
case T_ArrayExpr: /* other separators */
case T_CoalesceExpr: /* own parentheses */
case T_NullIfExpr: /* other separators */
case T_Aggref: /* own parentheses */
case T_Aggref: /* own parentheses */
case T_CaseExpr: /* other separators */
return true;
default:
@ -2610,7 +2610,7 @@ isSimpleNode(Node *node, Node *parentNode, int prettyFlags)
case T_ArrayExpr: /* other separators */
case T_CoalesceExpr: /* own parentheses */
case T_NullIfExpr: /* other separators */
case T_Aggref: /* own parentheses */
case T_Aggref: /* own parentheses */
case T_CaseExpr: /* other separators */
return true;
default:
@ -3026,6 +3026,11 @@ get_rule_expr(Node *node, deparse_context *context,
appendContextKeyword(context, "CASE",
0, PRETTYINDENT_VAR, 0);
if (caseexpr->arg)
{
appendStringInfoChar(buf, ' ');
get_rule_expr((Node *) caseexpr->arg, context, true);
}
foreach(temp, caseexpr->args)
{
CaseWhen *when = (CaseWhen *) lfirst(temp);
@ -3034,7 +3039,17 @@ get_rule_expr(Node *node, deparse_context *context,
appendStringInfoChar(buf, ' ');
appendContextKeyword(context, "WHEN ",
0, 0, 0);
get_rule_expr((Node *) when->expr, context, false);
if (caseexpr->arg)
{
/* Show only the RHS of "CaseTestExpr = RHS" */
Node *rhs;
Assert(IsA(when->expr, OpExpr));
rhs = (Node *) lsecond(((OpExpr *) when->expr)->args);
get_rule_expr(rhs, context, false);
}
else
get_rule_expr((Node *) when->expr, context, false);
appendStringInfo(buf, " THEN ");
get_rule_expr((Node *) when->result, context, true);
}