From 031c3e6d956b65722f27c3302323a9cbf09e9633 Mon Sep 17 00:00:00 2001
From: Christian Ramseyer <ramseyer@netnea.com>
Date: Fri, 31 Jan 2020 10:32:02 +0100
Subject: [PATCH] Optimize PortMAC query

* We meant well but it turns out that the array unnest and join is
  actually very slow, as the join arguments do not get pushed down
  into the CTE (in Postgres 9/10 at least, later versions remove some
  of the optimization barriers in that specifc type of query)
* This caused a seq scan on both device and device_port, and the query
  is executed many times during macsuck
* The query is now rewritten to use ANY (macaddr[]) and without CTE,
  which seems to be around 20x faster
---
 lib/App/Netdisco/DB/Result/Virtual/PortMacs.pm | 12 ++----------
 lib/App/Netdisco/Util/PortMAC.pm               |  2 +-
 2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/lib/App/Netdisco/DB/Result/Virtual/PortMacs.pm b/lib/App/Netdisco/DB/Result/Virtual/PortMacs.pm
index 3e29cb2e..212530d5 100644
--- a/lib/App/Netdisco/DB/Result/Virtual/PortMacs.pm
+++ b/lib/App/Netdisco/DB/Result/Virtual/PortMacs.pm
@@ -11,17 +11,9 @@ __PACKAGE__->table_class('DBIx::Class::ResultSource::View');
 __PACKAGE__->table("port_macs");
 __PACKAGE__->result_source_instance->is_virtual(1);
 __PACKAGE__->result_source_instance->view_definition(<<ENDSQL
-  SELECT dp.ip, dp.mac
-
-  FROM
-    (SELECT ip, mac FROM device
+    SELECT ip, mac FROM device where mac = any (?::macaddr[])
       UNION
-    SELECT ip, mac FROM device_port) dp
-
-  INNER JOIN
-    (SELECT unnest( ? ::macaddr[] )) locals(m)
-    ON (dp.mac = locals.m ::macaddr)
-
+    SELECT ip, mac FROM device_port dp where mac = any (?::macaddr[])
 ENDSQL
 );
 
diff --git a/lib/App/Netdisco/Util/PortMAC.pm b/lib/App/Netdisco/Util/PortMAC.pm
index 320d2b82..d3925938 100644
--- a/lib/App/Netdisco/Util/PortMAC.pm
+++ b/lib/App/Netdisco/Util/PortMAC.pm
@@ -37,7 +37,7 @@ sub get_port_macs {
 
     my $macs
         = schema('netdisco')->resultset('Virtual::PortMacs')->search({},
-        { bind => [$bindarray], select => [ 'mac', 'ip' ], group_by => [ 'mac', 'ip' ] } );
+        { bind => [$bindarray, $bindarray], select => [ 'mac', 'ip' ], group_by => [ 'mac', 'ip' ] } );
     my $cursor = $macs->cursor;
     while ( my @vals = $cursor->next ) {
         $port_macs->{ $vals[0] } = $vals[1];