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Reduce the size of the fmgr_builtin_oid_index[] array.

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This index array was originally defined to have 10000 entries (ranging
up to FirstGenbkiObjectId), but we really only need entries up to the
last existing builtin function OID, currently 6121.  That saves close
to 8K of never-accessed space in the server executable, at the small
price of one more fetch in fmgr_isbuiltin().

We could reduce the array size still further by renumbering a few of
the highest-numbered builtin functions; but there's a small risk of
breaking clients that have chosen to hardwire those function OIDs,
so it's not clear if it'd be worth the trouble.  (We should, however,
discourage future patches from choosing function OIDs above 6K as long
as there's still lots of space below that.)

Discussion: https://postgr.es/m/12359.1547063064@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2019-01-09 15:22:43 -05:00
parent 59029b6fb7
commit 8ff5f824dc
3 changed files with 19 additions and 21 deletions
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28
src/backend/utils/Gen_fmgrtab.pl
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@@ -80,11 +80,6 @@ foreach my $datfile (@input_files)
$catalog_data{$catname} = Catalog::ParseData($datfile, $schema, 0);
}
# Fetch some values for later.
my $FirstGenbkiObjectId =
Catalog::FindDefinedSymbol('access/transam.h', $include_path,
'FirstGenbkiObjectId');
# Collect certain fields from pg_proc.dat.
my @fmgr = ();
@@ -225,6 +220,7 @@ my %bmap;
$bmap{'t'} = 'true';
$bmap{'f'} = 'false';
my @fmgr_builtin_oid_index;
my $last_builtin_oid = 0;
my $fmgr_count = 0;
foreach my $s (sort { $a->{oid} <=> $b->{oid} } @fmgr)
{
@@ -232,6 +228,7 @@ foreach my $s (sort { $a->{oid} <=> $b->{oid} } @fmgr)
" { $s->{oid}, $s->{nargs}, $bmap{$s->{strict}}, $bmap{$s->{retset}}, \"$s->{prosrc}\", $s->{prosrc} }";
$fmgr_builtin_oid_index[ $s->{oid} ] = $fmgr_count++;
$last_builtin_oid = $s->{oid};
if ($fmgr_count <= $#fmgr)
{
@@ -244,31 +241,30 @@ foreach my $s (sort { $a->{oid} <=> $b->{oid} } @fmgr)
}
print $tfh "};\n";
print $tfh qq|
printf $tfh qq|
const int fmgr_nbuiltins = (sizeof(fmgr_builtins) / sizeof(FmgrBuiltin));
|;
const Oid fmgr_last_builtin_oid = %u;
|, $last_builtin_oid;
# Create fmgr_builtins_oid_index table.
#
# Note that the array has to be filled up to FirstGenbkiObjectId,
# as we can't rely on zero initialization as 0 is a valid mapping.
print $tfh qq|
const uint16 fmgr_builtin_oid_index[FirstGenbkiObjectId] = {
|;
printf $tfh qq|
const uint16 fmgr_builtin_oid_index[%u] = {
|, $last_builtin_oid + 1;
for (my $i = 0; $i < $FirstGenbkiObjectId; $i++)
for (my $i = 0; $i <= $last_builtin_oid; $i++)
{
my $oid = $fmgr_builtin_oid_index[$i];
# fmgr_builtin_oid_index is sparse, map nonexistant functions to
# fmgr_builtin_oid_index is sparse, map nonexistent functions to
# InvalidOidBuiltinMapping
if (not defined $oid)
{
$oid = 'InvalidOidBuiltinMapping';
}
if ($i + 1 == $FirstGenbkiObjectId)
if ($i == $last_builtin_oid)
{
print $tfh " $oid\n";
}