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Memory leak at server, when client select computed field, which used COALESCE or CAST [CORE6370] #6609

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firebird-automations opened this issue Jul 24, 2020 · 9 comments

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Submitted by: Jaromír Krys (fous)

I have table with 350 rows - random text:
CREATE TABLE TAB1
(
A1 Varchar(99),
A2 Varchar(199)
);
ALTER TABLE TAB1 ADD A3 COMPUTED BY (coalesce(a1, '')||'-'||coalesce(a2, ''));
and file try.sql:
SELECT a3 FROM tab1;
SELECT a3 FROM tab1;
... 5000 times
SELECT a3 FROM tab1;
I run command:
"c:\Program Files\Firebird\Firebird_3_0\isql.exe" -u SYSDBA -p 1 -i c:\1\try.sql -o c:\1\result.txt "localhost/3051:c:\fdb\try.fdb"
Then, if I observe the firebird server in the task manager, it gradually consumes more and more memory.
However, if I select column a1 (ie uncounted) instead of a3, then the memory consumption does not increase. Also, if the computed would not use coalesce, the consumed memory does not increase (or the consumption increases much more slowly - I'm not sure).
If I use a 2.5.8 server, the memory consumption also does not increase.
commit and new transaction - no change
disconnect and connect - memory is freed

Commits: dde597e

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Commented by: @cincuranet

I tested this on 3.0.5 x64 and I can confirm it as well.

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Commented by: @asfernandes

The leak happens even without data in the table?

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Commented by: Jaromír Krys (fous)

Yes, leak happens with empty table and 30 000 rows in try.sql

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Modified by: @asfernandes

assignee: Adriano dos Santos Fernandes [ asfernandes ]

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Commented by: @asfernandes

Thanks for the test case. Actually it's CAST that was leaking and COALESCE uses CAST internally.

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Modified by: @asfernandes

summary: Memory leak at server, when client select computed field, which used coalesce function => Memory leak at server, when client select computed field, which used COALESCE or CAST

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Modified by: @asfernandes

status: Open [ 1 ] => Resolved [ 5 ]

resolution: Fixed [ 1 ]

Fix Version: 3.0.7 [ 10940 ]

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Commented by: @asfernandes

Please test in the next v3 snapshot.

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Commented by: Jaromír Krys (fous)

Tested by try.sql - OK - many thanks
In real database - will be tested - not in snapshot

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