On 02/02/2014 08:54 PM, Craig Ringer wrote:
On 02/03/2014 09:09 AM, Craig Ringer wrote:
At a guess, we're looking at a case where a new child context is created
at every call, so every MemoryContextResetChildren call has to deal with
more child contexts.
That would be "yes". After a short run, I see 32849 lines like:
json_array_elements temporary cxt: 8192 total in 1 blocks; 8160 free (0
chunks); 32 used
under the context:
PortalMemory: 8192 total in 1 blocks
PortalHeapMemory: 7168 total in 3 blocks
ExecutorState: 65600 total in 4 blocks
ExprContext: 8192 total in 1 blocks
json_array_elements temporary cxt: 8192 total in 1 blocks;
8160 free (0 chunks); 32 used
The attached patch deletes the context after use, bringing performance
back into line. It should be backpatched to 9.3.
[...]
+ MemoryContextDelete(state->tmp_cxt);
+ state->tmp_cxt = NULL;
+
PG_RETURN_NULL();
Hmm. I guess I was assuming that the tmp_cxt would be cleaned up at the
end of the function since it's a child of the CurrentMemoryContext. But
if I got that wrong I'm happy to fix it. I don't see the point in
setting state->tmp_cxt to NULL since it's about to go out of scope anyway.
cheers
andrew
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