From c19615fe391c9577e2129fed4429736f6b5295da Mon Sep 17 00:00:00 2001 From: David Rowley Date: Tue, 30 Jul 2024 20:19:59 +1200 Subject: [PATCH] Disallow setting MAX_PARTITION_BUFFERS to less than 2 Add some comments to mention that this value must be at least 2 and also add a StaticAssertDecl to cause compilation failure if anyone tries to build with an invalid value. The multiInsertBuffers list must have at least two elements due to how the code in CopyMultiInsertInfoFlush() pushes the current ResultRelInfo's CopyMultiInsertBuffer to the end of the list. If the first element is also the last element, bad things will happen. Author: Zhang Mingli Discussion: https://postgr.es/m/CAApHDvpQ6t9ROcqbD-OgqR04Kfq4vQKw79Vo6r5j%2BciHwsSfkA%40mail.gmail.com --- src/backend/commands/copyfrom.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/src/backend/commands/copyfrom.c b/src/backend/commands/copyfrom.c index ce4d62e707c..c42a5621d5a 100644 --- a/src/backend/commands/copyfrom.c +++ b/src/backend/commands/copyfrom.c @@ -68,7 +68,10 @@ */ #define MAX_BUFFERED_BYTES 65535 -/* Trim the list of buffers back down to this number after flushing */ +/* + * Trim the list of buffers back down to this number after flushing. This + * must be >= 2. + */ #define MAX_PARTITION_BUFFERS 32 /* Stores multi-insert data related to a single relation in CopyFrom. */ @@ -550,6 +553,13 @@ CopyMultiInsertInfoFlush(CopyMultiInsertInfo *miinfo, ResultRelInfo *curr_rri, */ if (buffer->resultRelInfo == curr_rri) { + /* + * The code below would misbehave if we were trying to reduce the + * list to less than two items. + */ + StaticAssertDecl(MAX_PARTITION_BUFFERS >= 2, + "MAX_PARTITION_BUFFERS must be >= 2"); + miinfo->multiInsertBuffers = list_delete_first(miinfo->multiInsertBuffers); miinfo->multiInsertBuffers = lappend(miinfo->multiInsertBuffers, buffer); buffer = (CopyMultiInsertBuffer *) linitial(miinfo->multiInsertBuffers); -- 2.30.2