Re: Parallel index build for BRIN

Hi,

On 17.11.2024 11:28, Egor Rogov wrote:
> Hi everyone,
>
> This thread doesn't seem to have attracted attention, so let me try
> again. Two documentation pages claim that B-tree is the only access
> method that supports parallel building, which is no longer true. I
> propose to fix it in a way like this:
>
> diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
> index d54f9049569..b5b1580dee7 100644
> --- a/doc/src/sgml/config.sgml
> +++ b/doc/src/sgml/config.sgml
> @@ -2835,7 +2835,7 @@ include_dir 'conf.d'
>           Sets the maximum number of parallel workers that can be
>           started by a single utility command.  Currently, the parallel
>           utility commands that support the use of parallel workers are
> -         <command>CREATE INDEX</command> only when building a B-tree
> index,
> +         <command>CREATE INDEX</command> when building a B-tree or
> BRIN index,
>           and <command>VACUUM</command> without <literal>FULL</literal>
>           option.  Parallel workers are taken from the pool of processes
>           established by <xref linkend="guc-max-worker-processes"/>,
> limited
> diff --git a/doc/src/sgml/ref/create_index.sgml
> b/doc/src/sgml/ref/create_index.sgml
> index 621bc0e253c..208389e8006 100644
> --- a/doc/src/sgml/ref/create_index.sgml
> +++ b/doc/src/sgml/ref/create_index.sgml
> @@ -808,7 +808,7 @@ Indexes:
>     leveraging multiple CPUs in order to process the table rows faster.
>     This feature is known as <firstterm>parallel index
>     build</firstterm>.  For index methods that support building indexes
> -   in parallel (currently, only B-tree),
> +   in parallel (currently, B-tree and BRIN),
>     <varname>maintenance_work_mem</varname> specifies the maximum
>     amount of memory that can be used by each index build operation as
>     a whole, regardless of how many worker processes were started.

I've spotted another mention of B-tree being the only AM that supports
parallel builds: comment in src/backend/catalog/index.c. As this mention
is not visible to the users, I'd propose removing it altogether rather
than fixing it. Updated patch is attached.

>
> Thanks,
> Egor
>
>
> On 05.11.2024 12:12, Egor Rogov wrote:
>> Hi,
>>
>> Commit b4375717 introduced parallel CREATE INDEX for BRIN. I've
>> noticed that a couple of documentation pages need to be updated
>> accordingly. A small patch is attached.
>>
>> Thanks,
>> Egor