Memory leak on hashed agg rescan
I noticed a minor leak in the per-query context when ExecReScanAgg()
is called for a hashed aggregate. During rescan, build_hash_table() is
called to create a new empty hash table in the aggcontext. However,
build_hash_table() also constructs the "hash_needed" column list in
the per-query context, so repeated calls of build_hash_table() result
in leaking this memory for the duration of the query.
Attached is a patch that fixes this by only constructing "hash_needed"
if it doesn't already exist. I also bms_free'd the temporary BMS that
is created, although that's pretty harmless.
Neil
Attachments:
hashed_agg_mem_leak-1.patchapplication/octet-stream; name=hashed_agg_mem_leak-1.patchDownload+30-25
"Neil Conway" <neil.conway@gmail.com> writes:
I noticed a minor leak in the per-query context when ExecReScanAgg()
is called for a hashed aggregate. During rescan, build_hash_table() is
called to create a new empty hash table in the aggcontext. However,
build_hash_table() also constructs the "hash_needed" column list in
the per-query context, so repeated calls of build_hash_table() result
in leaking this memory for the duration of the query.
Attached is a patch that fixes this by only constructing "hash_needed"
if it doesn't already exist. I also bms_free'd the temporary BMS that
is created, although that's pretty harmless.
It would probably be cleaner to take that logic out of build_hash_table
altogether, and put it in a separate function to be called by
ExecInitAgg.
regards, tom lane
On Thu, Oct 16, 2008 at 5:26 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
It would probably be cleaner to take that logic out of build_hash_table
altogether, and put it in a separate function to be called by
ExecInitAgg.
Yeah, I considered that -- makes sense. Attached is the patch I
applied to HEAD, REL8_3_STABLE and REL8_2_STABLE.
Neil