Re: generate syscache info automatically

Peter Eisentraut <peter(at)eisentraut(dot)org> writes:

> The idea was mentioned in [0]. genbki.pl already knows everything about
> system catalog indexes. If we add a "please also make a syscache for
> this one" flag to the catalog metadata, we can have genbki.pl produce
> the tables in syscache.c and syscache.h automatically.

+1 on this worthwhile reduction of manual work. Tangentially, it
reminded me of one of my least favourite parts of Catalog.pm, the
regexes in ParseHeader():

> diff --git a/src/backend/catalog/Catalog.pm b/src/backend/catalog/Catalog.pm
> index 84aaeb002a..a727d692b7 100644
> --- a/src/backend/catalog/Catalog.pm
> +++ b/src/backend/catalog/Catalog.pm
> @@ -110,7 +110,7 @@ sub ParseHeader
> };
> }
> elsif (
> - /^DECLARE_(UNIQUE_)?INDEX(_PKEY)?\(\s*(\w+),\s*(\d+),\s*(\w+),\s*(.+)\)/
> + /^DECLARE_(UNIQUE_)?INDEX(_PKEY)?\(\s*(\w+),\s*(\d+),\s*(\w+),\s*(\w+),\s*(.+)\)/
> )
> {
> push @{ $catalog{indexing} },
> @@ -120,7 +120,8 @@ sub ParseHeader
> index_name => $3,
> index_oid => $4,
> index_oid_macro => $5,
> - index_decl => $6
> + table_name => $6,
> + index_decl => $7
> };
> }
> elsif (/^DECLARE_OID_DEFINING_MACRO\(\s*(\w+),\s*(\d+)\)/)

Now that we require Perl 5.14, we could replace this parenthesis-
counting nightmare with named captures (introduced in Perl 5.10), which
would make the above change look like this instead (context expanded to
show the whole elsif block):

elsif (
/^DECLARE_(UNIQUE_)?INDEX(_PKEY)?\(\s*
(?<index_name>\w+),\s*
(?<index_oid>\d+),\s*
(?<index_oid_macro>\w+),\s*
+ (?<table_name>\w+),\s*
(?<index_decl>.+)
\)/x
)
{
push @{ $catalog{indexing} },
{
is_unique => $1 ? 1 : 0,
is_pkey => $2 ? 1 : 0,
%+,
};
}

For other patterns without the optional bits in the keyword, it becomes
even simpler, e.g.

if (/^DECLARE_TOAST\(\s*
(?<parent_table>\w+),\s*
(?<toast_oid>\d+),\s*
(?<toast_index_oid>\d+)\s*
\)/x
)
{
push @{ $catalog{toasting} }, {%+};
}

I'd be happy to submit a patch to do this for all the ParseHeader()
regexes (in a separate thread) if others agree this is an improvement.

- ilmari