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Avoid aggregation which causes out-of-memory crashes in PostgreSQL

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The use of multiple string_agg functions, even if applied to groups
of one single record causes out of memory crashes in PG 9.3.4 for
some (large) tables.
This commit is contained in:
Javier Goizueta
2016-01-27 15:24:04 +01:00
parent 474de01757
commit b8d50204dd
1 changed files with 3 additions and 1 deletions
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4
scripts-available/CDB_Overviews.sql
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@@ -463,7 +463,9 @@ BEGIN
-- 'A', 'B', 'A', 'C', 'D' => 'A/B/C/...' -- 'A', 'B', 'A', 'C', 'D' => 'A/B/C/...'
-- Other ideas: if value is unique then use it, otherwise use something -- Other ideas: if value is unique then use it, otherwise use something
-- like '*' or '(varies)' or '(multiple values)', or NULL -- like '*' or '(varies)' or '(multiple values)', or NULL
RETURN 'CASE count(*) WHEN 1 THEN string_agg(' || qualified_column || ',''/'') ELSE ''*''' || ' END::' || column_type; -- Using 'string_agg(' || qualified_column || ',''/'')'
-- here causes
RETURN 'CASE count(*) WHEN 1 THEN MIN(' || qualified_column || ') ELSE NULL END::' || column_type;
ELSE ELSE
RETURN 'CASE count(*) WHEN 1 THEN MIN(' || qualified_column || ') ELSE NULL END::' || column_type; RETURN 'CASE count(*) WHEN 1 THEN MIN(' || qualified_column || ') ELSE NULL END::' || column_type;
END CASE; END CASE;