Jason Petersen <jason@citusdata.com> writes:
> Within the core codebase, BuildTupleFromCStrings is often called within a temporary memory context cleared after the
call.In dblink.c, this is justified as being needed to “[clean up] not only the data we have direct access to, but any
cruftthe I/O functions might leak”.
> I wrote a pretty minimal case to call BuildTupleFromCStrings in a loop (attached) and found that I was using 40GB of
RAMin a few minutes, though I was not allocating any memory myself and immediately freed the tuple it returned.
> Is the need to wrap this call in a protective context documented anywhere? Portions of the documentation use
BuildTupleFromCStringsin examples without mentioning this precaution. Is it just well-known, or did I miss a README or
commentsomewhere?
Most uses of BuildTupleFromCStrings only do it once per invocation of the
calling function, so that an outer-level reset of the calling function's
evaluation context is what takes care of any memory leaked by the I/O
functions BuildTupleFromCStrings invokes. If you intend to call it many
times within the same function call then you should use a context you can
reset between calls. This risk is hardly unique to BuildTupleFromCStrings,
which is why the documentation doesn't make a big point of it.
regards, tom lane