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Query with CASE and nested functions results in very long execution #2852

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monetdb-team opened this issue Nov 30, 2020 · 0 comments
Closed

Query with CASE and nested functions results in very long execution #2852

monetdb-team opened this issue Nov 30, 2020 · 0 comments

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@monetdb-team monetdb-team commented Nov 30, 2020

Date: 2011-08-07 17:06:11 +0200
From: Alfred Nordman <<alfred.nordman>>
To: SQL devs <>
Version: 11.3.7 (Apr2011-SP2) [obsolete]
CC: @njnes, @drstmane

Last updated: 2011-09-16 15:04:37 +0200

Comment 16087

Date: 2011-08-07 17:06:11 +0200
From: Alfred Nordman <<alfred.nordman>>

User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/13.0.782.107 Safari/535.1
Build Identifier:

SQL statement with case division and embedded functions compiles about 2 minutes on my computer. If I change "/" to "*" everything is executed immediately.

Reproducible: Always

Steps to Reproduce:

1.CREATE TABLE t (c INT);
2.INSERT INTO t VALUES (0);
3.explain SELECT
COALESCE(
COALESCE("c" /
CASE
WHEN COALESCE("c" , 0) = 0
THEN
NULL
END
, 0) - COALESCE("c" /
CASE
WHEN "c" = 0
THEN
NULL
END
,0)
, 0)
FROM
t
;

Actual Results:

Very long compilation time. It looks like generated MAL code is not correct

Expected Results:

I guess that this script must be compiled immediately

I managed to simplify my initial script which hanged the computer to this test case. Further simplifications lead to immediate execution.
The result of this script does not have any sense it is only test sample

Comment 16113

Date: 2011-08-19 16:29:20 +0200
From: @njnes

fixed. The long execution time was caused by recusive inplace modifing the relational tree

Comment 16128

Date: 2011-08-22 08:17:06 +0200
From: @drstmane

We should consider adding a test (also) for this one.

Comment 16135

Date: 2011-08-22 16:41:13 +0200
From: @drstmane

Changeset fa813932a753 made by Stefan Manegold Stefan.Manegold@cwi.nl in the MonetDB repo, refers to this bug.

For complete details, see http//devmonetdborg/hg/MonetDB?cmd=changeset;node=fa813932a753

Changeset description:

added tests for bug #2852 & bug #2862

Comment 16247

Date: 2011-09-16 15:04:37 +0200
From: @sjoerdmullender

The Aug2011 version has been released.

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