Re: [HACKERS] Query fails when SRFs are part of FROM clause (Commitid: 69f4b9c85f)
От | David G. Johnston |
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Тема | Re: [HACKERS] Query fails when SRFs are part of FROM clause (Commitid: 69f4b9c85f) |
Дата | |
Msg-id | CAKFQuwagEp+crYYadtStn5_G-WcM=7uFBEwK5z79RF2dYTViWQ@mail.gmail.com обсуждение исходный текст |
Ответ на | [HACKERS] Query fails when SRFs are part of FROM clause (Commit id: 69f4b9c85f) (Rushabh Lathia <rushabh.lathia@gmail.com>) |
Ответы |
Re: [HACKERS] Query fails when SRFs are part of FROM clause (Commitid: 69f4b9c85f)
Re: [HACKERS] Query fails when SRFs are part of FROM clause (Commitid: 69f4b9c85f) |
Список | pgsql-hackers |
Consider the below test;CREATE TABLE tab ( a int primary key);SELECT *FROM pg_constraint pc,CAST(CASE WHEN pc.contype IN ('f','u','p') THEN generate_series(1, array_upper(pc.conkey, 1)) ELSE NULL END AS int) AS position;Above query is failing with "set-valued function called in context that cannotaccept a set". But if I remove the CASE from the query then it working just good.Like:SELECT *FROM pg_constraint pc,CAST(generate_series(1, array_upper(pc.conkey, 1)) AS int) AS position;This started failing with 69f4b9c85f168ae006929eec44fc44d569e846b9. It seems check_srf_call_placement() sets the hasTargetSRFs flag and but when the SRFsat the rtable ofcourse this flag doesn't get set. It seems like missing somethingtheir, but I might be completely wrong as not quire aware of this area.
I'm a bit surprised that your query actually works...and without delving into source code its hard to explain why it should/shouldn't or whether the recent SRF work was intended to impact it.
In any case the more idiomatic way of writing your query these days (since 9.4 came out) is:
SELECT *
FROM pg_constraint pc
LEFT JOIN LATERAL generate_series(1, case when contype in ('f','p','u') then array_upper(pc.conkey, 1) else 0 end) gs ON true;
generate_series is smart enough to return an empty set (instead of erroring out) when provided with (1,0) as arguments.
David J.
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