Re: [Proposal] Global temporary tables

> 2020年2月2日 上午2:00，Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> 写道：
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> so 1. 2. 2020 v 14:39 odesílatel 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com <mailto:wenjing(dot)zwj(at)alibaba-inc(dot)com>> napsal:
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>> 2020年1月30日 下午10:21，Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com <mailto:pavel(dot)stehule(at)gmail(dot)com>> 写道：
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>> čt 30. 1. 2020 v 15:17 odesílatel 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com <mailto:wenjing(dot)zwj(at)alibaba-inc(dot)com>> napsal:
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>> > 2020年1月29日 下午9:48，Robert Haas <robertmhaas(at)gmail(dot)com <mailto:robertmhaas(at)gmail(dot)com>> 写道：
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>> > On Tue, Jan 28, 2020 at 12:12 PM 曾文旌(义从) <wenjing(dot)zwj(at)alibaba-inc(dot)com <mailto:wenjing(dot)zwj(at)alibaba-inc(dot)com>> wrote:
>> >>> Opinion by Pavel
>> >>> + rel->rd_islocaltemp = true; <<<<<<< if this is valid, then the name of field "rd_islocaltemp" is not probably best
>> >>> I renamed rd_islocaltemp
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>> >> I don't see any change?
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>> >> Rename rd_islocaltemp to rd_istemp in global_temporary_table_v8-pg13.patch
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>> > In view of commit 6919b7e3294702adc39effd16634b2715d04f012, I think
>> > that this has approximately a 0% chance of being acceptable. If you're
>> > setting a field in a way that is inconsistent with the current use of
>> > the field, you're probably doing it wrong, because the field has an
>> > existing purpose to which new code must conform. And if you're not
>> > doing that, then you don't need to rename it.
>> Thank you for pointing it out.
>> I've rolled back the rename.
>> But I still need rd_localtemp to be true, The reason is that
>> 1 GTT The GTT needs to support DML in read-only transactions ,like local temp table.
>> 2 GTT does not need to hold the lock before modifying the index buffer ,also like local temp table.
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>> Please give me feedback.
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>> maybe some like
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>> rel->rd_globaltemp = true;
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>> and somewhere else
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>> if (rel->rd_localtemp || rel->rd_globaltemp)
>> {
>> ...
>> }
> I tried to optimize code in global_temporary_table_v10-pg13.patch
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> Please give me feedback.
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> I tested this patch and I have not any objections - from my user perspective it is work as I expect
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> +#define RELATION_IS_TEMP(relation) \
> + ((relation)->rd_islocaltemp || \
> + (relation)->rd_rel->relpersistence == RELPERSISTENCE_GLOBAL_TEMP)
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> It looks little bit unbalanced
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> maybe is better to inject rd_isglobaltemp to relation structure
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> and then
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> it should to like
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> +#define RELATION_IS_TEMP(relation) \
> + ((relation)->rd_islocaltemp || \
> + (relation)->rd_isglobaltemp))
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> But I have not idea if it helps in complex
In my opinion
For local temp table we need (relation)->rd_rel->relpersistence == RELPERSISTENCE_TEMP
and because one local temp table belongs to only one session, need to mark one sessions rd_islocaltemp = true ,and other to rd_islocaltemp = false.

But For GTT, just need (relation)->rd_rel->relpersistence == RELPERSISTENCE_GLOBAL_GLOBAL_TEMP
One GTT can be used for every session, so no need rd_isglobaltemp anymore. This seems duplicated and redundant.

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> Wenjing
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>> Wenjing
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>> >
>> > --
>> > Robert Haas
>> > EnterpriseDB: http://www.enterprisedb.com <http://www.enterprisedb.com/>
>> > The Enterprise PostgreSQL Company
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