Re: [HACKERS] plpgsql - additional extra checks

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От Pavel Stehule
Тема Re: [HACKERS] plpgsql - additional extra checks
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Msg-id CAFj8pRCv0DSwyHX0d1GiADvgC1LELGJ2H_r=RMox_TN_X9mMAw@mail.gmail.com
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Ответ на Re: [HACKERS] plpgsql - additional extra checks  (Jim Nasby <Jim.Nasby@BlueTreble.com>)
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2017-01-13 2:46 GMT+01:00 Jim Nasby <Jim.Nasby@bluetreble.com>:
On 1/11/17 5:54 AM, Pavel Stehule wrote:
+    <term><varname>too_many_rows</varname></term>
+    <listitem>
+     <para>
+      When result is assigned to a variable by <literal>INTO</literal> clause,
+      checks if query returns more than one row. In this case the assignment
+      is not deterministic usually - and it can be signal some issues in design.

Shouldn't this also apply to

var := blah FROM some_table WHERE ...;

yes, it is possible.

I am not sure - how to document it. This pattern is undocumented and it is side effect of our parser.

If somebody use var := (SELECT xxx FROM ..)

what is correct syntax, then exactly only one row is required.

But the extra check is ok, if we technically allows this syntax.

Regards

Pavel


?

AIUI that's one of the beefs the plpgsql2 project has.

FWIW, I'd also be in favor of a NOMULTI option to INTO, but I don't see any way to do something like that with var := blah FROM.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com
855-TREBLE2 (855-873-2532)

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