From: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Refactor construct_array() and deconstruct_array() for built-in types
Date: Fri, 01 Jul 2022 11:43:21 +0100
Message-ID: <871qv5kt9y.fsf@wibble.ilmari.org> (raw)
In-Reply-To: <c030a2ef-02d6-ccdb-8ebe-bc97df69be59@enterprisedb.com>
References: <2914356f-9e5f-8c59-2995-5997fc48bcba@enterprisedb.com>
<1844517.1651502932@sss.pgh.pa.us>
<c030a2ef-02d6-ccdb-8ebe-bc97df69be59@enterprisedb.com>
Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> On 02.05.22 16:48, Tom Lane wrote:
>> Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
>>> There are many calls to construct_array() and deconstruct_array() for
>>> built-in types, for example, when dealing with system catalog columns.
>>> These all hardcode the type attributes necessary to pass to these functions.
>>
>>> To simplify this a bit, add construct_array_builtin(),
>>> deconstruct_array_builtin() as wrappers that centralize this hardcoded
>>> knowledge. This simplifies many call sites and reduces the amount of
>>> hardcoded stuff that is spread around.
>>
>>> I also considered having genbki.pl generate lookup tables for these
>>> hardcoded values, similar to schemapg.h, but that ultimately seemed
>>> excessive.
>> +1 --- the added overhead of the switch statements is probably a
>> reasonable price to pay for the notational simplification and
>> bug-proofing.
>> One minor coding gripe is that compilers that don't know that
>> elog(ERROR)
>> doesn't return will certainly generate "use of possibly-uninitialized
>> variable" complaints. Suggest inserting "return NULL;" or similar into
>> the default: cases. I'd also use more specific error wording to help
>> people find where they need to add code when they make use of a new type;
>> maybe like "type %u not supported by construct_array_builtin".
>
> I have pushed this with the improvements you had suggested.
I dind't pay much attention to this thread earlier, but I was struck by
the duplication of the switch statement determining the elemlen,
elembyval, and elemalign values between the construct and deconstruct
functions. How about a common function they can both call? Something
like:
static void builtin_type_details(Oid elemtype,
int *elemlen,
bool *elembyval,
char *elemalign);
- ilmari
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To: pgsql-hackers@postgresql.org
Cc: ilmari@ilmari.org, peter.eisentraut@enterprisedb.com, tgl@sss.pgh.pa.us
Subject: Re: Refactor construct_array() and deconstruct_array() for built-in types
In-Reply-To: <871qv5kt9y.fsf@wibble.ilmari.org>
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