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Fix memory leak in Incremental Sort rescans 

The Incremental Sort had a couple issues, resulting in leaking memory
during rescans, possibly triggering OOM. The code had a couple of
related flaws:

1. During rescans, the sort states were reset but then also set to NULL
   (despite the comment saying otherwise). ExecIncrementalSort then
   sees NULL and initializes a new sort state, leaking the memory used
   by the old one.

2. Initializing the sort state also automatically rebuilt the info about
   presorted keys, leaking the already initialized info. presorted_keys
   was also unnecessarily reset to NULL.

Patch by James Coleman, based on patches by Laurenz Albe and Tom Lane.
Backpatch to 13, where Incremental Sort was introduced.

Author: James Coleman, Laurenz Albe, Tom Lane
Reported-by: Laurenz Albe, Zu-Ming Jiang
Backpatch-through: 13
Discussion: https://postgr.es/m/b2bd02dff61af15e3526293e2771f874cf2a3be7.camel%40cybertec.at
Discussion: https://postgr.es/m/db03c582-086d-e7cd-d4a1-3bc722f81765%40inf.ethz.ch
This commit is contained in:
Tomas Vondra 2023-07-02 18:54:09 +02:00
parent 537b70b82c
commit 3ce761d5ca
1 changed files with 0 additions and 7 deletions
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7
src/backend/executor/nodeIncrementalSort.c
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@ -1138,7 +1138,6 @@ ExecReScanIncrementalSort(IncrementalSortState *node)
node->outerNodeDone = false;
node->n_fullsort_remaining = 0;
node->bound_Done = 0;
node->presorted_keys = NULL;
node->execution_status = INCSORT_LOADFULLSORT;
@ -1151,15 +1150,9 @@ ExecReScanIncrementalSort(IncrementalSortState *node)
* cause a leak.
*/
if (node->fullsort_state != NULL)
{
tuplesort_reset(node->fullsort_state);
node->fullsort_state = NULL;
}
if (node->prefixsort_state != NULL)
{
tuplesort_reset(node->prefixsort_state);
node->prefixsort_state = NULL;
}
/*
* If chgParam of subnode is not null, theni the plan will be re-scanned