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Disable prepared statements completely

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Because of the way DBIx::Class does prepared statements, even
innocuous queries such

  $c->model('DB::Builds)->search({finished => 0})

can be extremely slow.  This is because DBIx::Class prepares a
PostgreSQL statement

  select ... from Builds where finished = ?

and since Builds is very large and there is a large fraction of rows
with "finished = 1", the PostgreSQL query planner decides to implement
this query with a sequential scan of the Builds table (despite the
existence of an index on "finished"), which is extremely slow.  It
would be nice if we could tell DBIx::Class that constants should be
part of the prepared statement, i.e.

  select ... from Builds where finished = 0

but AFAIK we can't.
This commit is contained in:
Eelco Dolstra
2012-03-12 19:42:59 +01:00
parent 2d1cf73974
commit abe71a767b
2 changed files with 9 additions and 10 deletions
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14
src/lib/Hydra/Controller/Root.pm
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@ -95,15 +95,11 @@ sub timeline :Local {
sub status :Local {
my ($self, $c) = @_;
$c->model('DB')->storage->dbh_do(sub {
my (undef, $dbh) = @_;
local $dbh->{pg_server_prepare} = 0;
$c->stash->{steps} = [ $c->model('DB::BuildSteps')->search(
{ 'me.busy' => 1, 'build.finished' => 0, 'build.busy' => 1 },
{ join => [ 'build' ]
, order_by => [ 'machine' ]
} ) ];
});
$c->stash->{steps} = [ $c->model('DB::BuildSteps')->search(
{ 'me.busy' => 1, 'build.finished' => 0, 'build.busy' => 1 },
{ join => [ 'build' ]
, order_by => [ 'machine' ]
} ) ];
}