From 5492f6a2b814d01ad50a9d7e07f41db09ba77be1 Mon Sep 17 00:00:00 2001
From: Hubert depesz Lubaczewski <depesz@depesz.com>
Date: Mon, 7 Mar 2022 13:15:51 +0100
Subject: [PATCH] Dont use cursor for getting plans

Cursors cause bug in Pg15
---
 scripts/find_interesting_plans | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/scripts/find_interesting_plans b/scripts/find_interesting_plans
index d0f22fd..ab5a3fb 100755
--- a/scripts/find_interesting_plans
+++ b/scripts/find_interesting_plans
@@ -68,11 +68,12 @@ for my $partno ( 0 .. $#{ $partitions } ) {
     my $errors      = 0;
     my $interesting = 0;
 
-    my $query = sprintf "select id, plan FROM %s WHERE is_public and NOT is_deleted and NOT is_anonymized and plan ~ 'actual time=[0-9]'", $part;
-    $dbh->do( "DECLARE csr CURSOR FOR $query" );
+    my $prev_id = '';
+    my $query   = sprintf "select id, plan FROM %s WHERE is_public and NOT is_deleted and NOT is_anonymized and plan ~ 'actual time=[0-9]' AND id > ? order by ID ASC LIMIT 100", $part;
     while ( 1 ) {
-        my $rows = $dbh->selectall_arrayref( 'FETCH 100 FROM csr', { 'Slice' => {} } );
+        my $rows = $dbh->selectall_arrayref( $query, { 'Slice' => {} }, $prev_id );
         last if 0 == scalar @{ $rows };
+        $prev_id = $rows->[ -1 ]->{ 'id' };
         for my $row ( @{ $rows } ) {
             $seen++;
             my $explain;
@@ -88,8 +89,8 @@ for my $partno ( 0 .. $#{ $partitions } ) {
 
             my $is_interesting = 0;
 
-            for my $line ( @{ output_lines( $row->{'id'}, $explain ) } ) {
-                print $out join("\t", @{$line}) . "\n";
+            for my $line ( @{ output_lines( $row->{ 'id' }, $explain ) } ) {
+                print $out join( "\t", @{ $line } ) . "\n";
                 $is_interesting = 1;
             }
 
@@ -111,7 +112,8 @@ exit;
 
 sub output_lines {
     my ( $id, $plan ) = @_;
-    my $ret = [];
+    my $ret      = [];
+    my $plan_len = length( $plan->source );
     for my $node ( $plan->top_node, $plan->top_node->all_recursive_subnodes ) {
 
         next unless $node->estimated_row_width;
@@ -120,16 +122,17 @@ sub output_lines {
         next unless $node->extra_info;
 
         # At least 3 pages worth of data is returned
-        next unless $node->total_rows * $node->estimated_row_width > 3 * 8192;
+        next unless ( $node->total_rows + $node->total_rows_removed ) * $node->estimated_row_width > 3 * 8192;
 
         # At least 90% of rows were removed
-        next unless $node->total_rows_removed > 9 * $node->total_rows;
+        next unless $node->total_rows_removed > 2 * $node->total_rows;
 
         my @filter_lines = grep { /^Filter:/ } @{ $node->extra_info };
+
         # There are filter expressions
         next if 0 == scalar @filter_lines;
 
-        push @{ $ret }, map { [ $id, $node->id, $node->type, $node->estimated_row_width, $node->total_rows, $node->total_rows_removed, $_ ] } @filter_lines;
+        push @{ $ret }, map { [ $id, $plan_len, $node->type, $_ ] } @filter_lines;
     }
     return $ret;
 }