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Fix memory leaks in PL/Python.

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Previously, plpython was in the habit of allocating a lot of stuff in
TopMemoryContext, and it was very slipshod about making sure that stuff
got cleaned up; in particular, use of TopMemoryContext as fn_mcxt for
function calls represents an unfixable leak, since we generally don't
know what the called function might have allocated in fn_mcxt.  This
results in session-lifespan leakage in certain usage scenarios, as for
example in a case reported by Ed Behn back in July.

To fix, get rid of all the retail allocations in TopMemoryContext.
All long-lived allocations are now made in sub-contexts that are
associated with specific objects (either pl/python procedures, or
Python-visible objects such as cursors and plans).  We can clean these
up when the associated object is deleted.

I went so far as to get rid of PLy_malloc completely.  There were a
couple of places where it could still have been used safely, but on
the whole it was just an invitation to bad coding.

Haribabu Kommi, based on a draft patch by Heikki Linnakangas;
some further work by me
This commit is contained in:
Tom Lane
2015-11-05 13:52:30 -05:00
parent 64b2e7ad91
commit 8c75ad436f
15 changed files with 222 additions and 224 deletions
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39
src/pl/plpython/plpy_main.c
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@ -277,7 +277,12 @@ plpython_inline_handler(PG_FUNCTION_ARGS)
flinfo.fn_mcxt = CurrentMemoryContext;
MemSet(&proc, 0, sizeof(PLyProcedure));
proc.pyname = PLy_strdup("__plpython_inline_block");
proc.mcxt = AllocSetContextCreate(TopMemoryContext,
"__plpython_inline_block",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
proc.pyname = MemoryContextStrdup(proc.mcxt, "__plpython_inline_block");
proc.langid = codeblock->langOid;
proc.result.out.d.typoid = VOIDOID;
@ -364,17 +369,32 @@ PLy_current_execution_context(void)
return PLy_execution_contexts;
}
MemoryContext
PLy_get_scratch_context(PLyExecutionContext *context)
{
/*
* A scratch context might never be needed in a given plpython procedure,
* so allocate it on first request.
*/
if (context->scratch_ctx == NULL)
context->scratch_ctx =
AllocSetContextCreate(TopTransactionContext,
"PL/Python scratch context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
return context->scratch_ctx;
}
static PLyExecutionContext *
PLy_push_execution_context(void)
{
PLyExecutionContext *context = PLy_malloc(sizeof(PLyExecutionContext));
PLyExecutionContext *context;
context = (PLyExecutionContext *)
MemoryContextAlloc(TopTransactionContext, sizeof(PLyExecutionContext));
context->curr_proc = NULL;
context->scratch_ctx = AllocSetContextCreate(TopTransactionContext,
"PL/Python scratch context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
context->scratch_ctx = NULL;
context->next = PLy_execution_contexts;
PLy_execution_contexts = context;
return context;
@ -390,6 +410,7 @@ PLy_pop_execution_context(void)
PLy_execution_contexts = context->next;
MemoryContextDelete(context->scratch_ctx);
PLy_free(context);
if (context->scratch_ctx)
MemoryContextDelete(context->scratch_ctx);
pfree(context);
}