Re: [bug fix] Memory leak in dblink - Mailing list pgsql-hackers

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On 06/18/2014 07:29 PM, Tom Lane wrote:
> I wrote:
>> I do see growth in the per-query context as well.  I'm not sure 
>> where that's coming from, but we probably should try to find
>> out. A couple hundred bytes per iteration is going to add up,
>> even if it's not as fast as 8K per iteration.  I'm not sure it's
>> dblink's fault, because I don't see anything in dblink.c that is
>> allocating anything in the per-query context, except for the
>> returned tuplestores, which somebody else should clean up.
> 
> I poked at this example some more, and found that the additional
> memory leak is occurring during evaluation of the arguments to be
> passed to dblink().  There's been a comment there for a very long
> time suggesting that we might need to do something about that ...
> 
> With the attached patch on top of yours, I see no leak anymore.

I can confirm that -- rock solid with 1 million iterations. I assume
that should not be back-patched though?

On a side note, while perusing this section of code:

8<-------------------------- at dblink.c:1176 --------------------------/* make sure we have a persistent copy of the
tupdesc*/tupdesc = CreateTupleDescCopy(tupdesc);
 
/* check result and tuple descriptor have the same number of columns */if (nfields != tupdesc->natts)    ereport(ERROR,
          (errcode(ERRCODE_DATATYPE_MISMATCH),             errmsg("remote query result rowtype does not match "
   "the specified FROM clause rowtype")));
 
/* Prepare attinmeta for later data conversions */sinfo->attinmeta = TupleDescGetAttInMetadata(tupdesc);
/* Create a new, empty tuplestore */oldcontext =
MemoryContextSwitchTo(rsinfo->econtext->ecxt_per_query_memory);sinfo->tuplestore= tuplestore_begin_heap(true, false,
work_mem);rsinfo->setResult= sinfo->tuplestore;rsinfo->setDesc = tupdesc;MemoryContextSwitchTo(oldcontext);
 
8<-------------------------- at dblink.c:1194 --------------------------

Shouldn't that CreateTupleDescCopy() happen in ecxt_per_query_memory?

Joe

- -- 
Joe Conway
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