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Adjust constant-folding of CASE expressions so that the simple comparison

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form of CASE (eg, CASE 0 WHEN 1 THEN ...) can be constant-folded as it
was in 7.4.  Also, avoid constant-folding result expressions that are
certainly unreachable --- the former coding was a bit cavalier about this
and could generate unexpected results for all-constant CASE expressions.
Add regression test cases.  Per report from Vlad Marchenko.
This commit is contained in:
Tom Lane
2005-02-02 21:49:09 +00:00
parent b3a7e987a1
commit fffb5819ca
3 changed files with 107 additions and 40 deletions
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17
src/test/regress/expected/case.out
View File

@@ -72,6 +72,23 @@ SELECT '6' AS "One",
6 | 6
(1 row)
-- Constant-expression folding shouldn't evaluate unreachable subexpressions
SELECT CASE WHEN 1=0 THEN 1/0 WHEN 1=1 THEN 1 ELSE 2/0 END;
case
------
1
(1 row)
SELECT CASE 1 WHEN 0 THEN 1/0 WHEN 1 THEN 1 ELSE 2/0 END;
case
------
1
(1 row)
-- However we do not currently suppress folding of potentially
-- reachable subexpressions
SELECT CASE WHEN i > 100 THEN 1/0 ELSE 0 END FROM case_tbl;
ERROR: division by zero
-- Test for cases involving untyped literals in test expression
SELECT CASE 'a' WHEN 'a' THEN 1 ELSE 2 END;
case

8
src/test/regress/sql/case.sql
View File

@@ -58,6 +58,14 @@ SELECT '6' AS "One",
ELSE 7
END AS "Two WHEN with default";
-- Constant-expression folding shouldn't evaluate unreachable subexpressions
SELECT CASE WHEN 1=0 THEN 1/0 WHEN 1=1 THEN 1 ELSE 2/0 END;
SELECT CASE 1 WHEN 0 THEN 1/0 WHEN 1 THEN 1 ELSE 2/0 END;
-- However we do not currently suppress folding of potentially
-- reachable subexpressions
SELECT CASE WHEN i > 100 THEN 1/0 ELSE 0 END FROM case_tbl;
-- Test for cases involving untyped literals in test expression
SELECT CASE 'a' WHEN 'a' THEN 1 ELSE 2 END;