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c/driver/postgresql: infer schema by using a prepared statement #701

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lidavidm opened this issue May 23, 2023 · 1 comment · Fixed by #707
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c/driver/postgresql: infer schema by using a prepared statement #701

lidavidm opened this issue May 23, 2023 · 1 comment · Fixed by #707
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@lidavidm
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ADBC Libraries 0.5.0

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@lidavidm
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Would this have an impact on performance or server resources?

pqDescribePrepared gives you the columns of the result schema. That lets us infer the schema without the current SELECT (*) LIMIT 0 hack, which breaks down for things that aren't SELECTs.
@lidavidm lidavidm added this to the ADBC Libraries 0.5.0 milestone May 23, 2023
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I will probably do this first since the C++ equivalent of #700 would get much easier with this.

lidavidm added a commit to lidavidm/arrow-adbc that referenced this issue May 24, 2023
@lidavidm
feat(c/driver/postgresql): handle non-SELECT statements
ac943c5 
Before we tried to infer the query schema before COPY by wrapping
it in a "SELECT * FROM (...) LIMIT 0".  This broke if the query
was (for example) a CREATE or UPDATE.  Instead, use a prepared
statement to infer instead.  If we find that there are no result
columns, then execute without the COPY path.

Also, test what happens with "INSERT INTO ... RETURNING" (this
works with COPY).

Fixes apache#701.
@lidavidm lidavidm self-assigned this May 24, 2023
@lidavidm lidavidm mentioned this issue May 24, 2023
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lidavidm added a commit that referenced this issue May 25, 2023
@lidavidm
feat(c/driver/postgresql): handle non-SELECT statements (#707)
a6bd37a 
Before we tried to infer the query schema before COPY by wrapping it in
a "SELECT * FROM (...) LIMIT 0". This broke if the query was (for
example) a CREATE or UPDATE. Instead, use a prepared statement to infer
instead. If we find that there are no result columns, then execute
without the COPY path.

Also, test what happens with "INSERT INTO ... RETURNING" (this works
with COPY).

Fixes #701.
@lidavidm lidavidm mentioned this issue Jun 9, 2023
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feat(c/driver/postgresql): handle non-SELECT statements lidavidm/arrow-adbc
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