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Fix memory leaks in PL/Python.
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
1 parent 64b2e7a commit 8c75ad4

15 files changed

+221
-223
lines changed

‎src/pl/plpython/plpy_cursorobject.c

Lines changed: 21 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,7 @@
88

99
#include "access/xact.h"
1010
#include "mb/pg_wchar.h"
11+
#include "utils/memutils.h"
1112

1213
#include "plpython.h"
1314

@@ -111,7 +112,12 @@ PLy_cursor_query(const char *query)
111112
return NULL;
112113
cursor->portalname = NULL;
113114
cursor->closed = false;
114-
PLy_typeinfo_init(&cursor->result);
115+
cursor->mcxt = AllocSetContextCreate(TopMemoryContext,
116+
"PL/Python cursor context",
117+
ALLOCSET_DEFAULT_MINSIZE,
118+
ALLOCSET_DEFAULT_INITSIZE,
119+
ALLOCSET_DEFAULT_MAXSIZE);
120+
PLy_typeinfo_init(&cursor->result, cursor->mcxt);
115121

116122
oldcontext = CurrentMemoryContext;
117123
oldowner = CurrentResourceOwner;
@@ -139,7 +145,7 @@ PLy_cursor_query(const char *query)
139145
elog(ERROR, "SPI_cursor_open() failed: %s",
140146
SPI_result_code_string(SPI_result));
141147

142-
cursor->portalname = PLy_strdup(portal->name);
148+
cursor->portalname = MemoryContextStrdup(cursor->mcxt, portal->name);
143149

144150
PLy_spi_subtransaction_commit(oldcontext, oldowner);
145151
}
@@ -200,7 +206,12 @@ PLy_cursor_plan(PyObject *ob, PyObject *args)
200206
return NULL;
201207
cursor->portalname = NULL;
202208
cursor->closed = false;
203-
PLy_typeinfo_init(&cursor->result);
209+
cursor->mcxt = AllocSetContextCreate(TopMemoryContext,
210+
"PL/Python cursor context",
211+
ALLOCSET_DEFAULT_MINSIZE,
212+
ALLOCSET_DEFAULT_INITSIZE,
213+
ALLOCSET_DEFAULT_MAXSIZE);
214+
PLy_typeinfo_init(&cursor->result, cursor->mcxt);
204215

205216
oldcontext = CurrentMemoryContext;
206217
oldowner = CurrentResourceOwner;
@@ -261,7 +272,7 @@ PLy_cursor_plan(PyObject *ob, PyObject *args)
261272
elog(ERROR, "SPI_cursor_open() failed: %s",
262273
SPI_result_code_string(SPI_result));
263274

264-
cursor->portalname = PLy_strdup(portal->name);
275+
cursor->portalname = MemoryContextStrdup(cursor->mcxt, portal->name);
265276

266277
PLy_spi_subtransaction_commit(oldcontext, oldowner);
267278
}
@@ -315,12 +326,13 @@ PLy_cursor_dealloc(PyObject *arg)
315326

316327
if (PortalIsValid(portal))
317328
SPI_cursor_close(portal);
329+
cursor->closed = true;
330+
}
331+
if (cursor->mcxt)
332+
{
333+
MemoryContextDelete(cursor->mcxt);
334+
cursor->mcxt = NULL;
318335
}
319-
320-
PLy_free(cursor->portalname);
321-
cursor->portalname = NULL;
322-
323-
PLy_typeinfo_dealloc(&cursor->result);
324336
arg->ob_type->tp_free(arg);
325337
}
326338

‎src/pl/plpython/plpy_cursorobject.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -14,6 +14,7 @@ typedef struct PLyCursorObject
1414
char *portalname;
1515
PLyTypeInfo result;
1616
bool closed;
17+
MemoryContext mcxt;
1718
} PLyCursorObject;
1819

1920
extern void PLy_cursor_init_type(void);

‎src/pl/plpython/plpy_exec.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -852,6 +852,6 @@ PLy_abort_open_subtransactions(int save_subxact_level)
852852

853853
MemoryContextSwitchTo(subtransactiondata->oldcontext);
854854
CurrentResourceOwner = subtransactiondata->oldowner;
855-
PLy_free(subtransactiondata);
855+
pfree(subtransactiondata);
856856
}
857857
}

‎src/pl/plpython/plpy_main.c

Lines changed: 30 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -277,7 +277,12 @@ plpython_inline_handler(PG_FUNCTION_ARGS)
277277
flinfo.fn_mcxt = CurrentMemoryContext;
278278

279279
MemSet(&proc, 0, sizeof(PLyProcedure));
280-
proc.pyname = PLy_strdup("__plpython_inline_block");
280+
proc.mcxt = AllocSetContextCreate(TopMemoryContext,
281+
"__plpython_inline_block",
282+
ALLOCSET_DEFAULT_MINSIZE,
283+
ALLOCSET_DEFAULT_INITSIZE,
284+
ALLOCSET_DEFAULT_MAXSIZE);
285+
proc.pyname = MemoryContextStrdup(proc.mcxt, "__plpython_inline_block");
281286
proc.langid = codeblock->langOid;
282287
proc.result.out.d.typoid = VOIDOID;
283288

@@ -364,17 +369,32 @@ PLy_current_execution_context(void)
364369
return PLy_execution_contexts;
365370
}
366371

372+
MemoryContext
373+
PLy_get_scratch_context(PLyExecutionContext *context)
374+
{
375+
/*
376+
* A scratch context might never be needed in a given plpython procedure,
377+
* so allocate it on first request.
378+
*/
379+
if (context->scratch_ctx == NULL)
380+
context->scratch_ctx =
381+
AllocSetContextCreate(TopTransactionContext,
382+
"PL/Python scratch context",
383+
ALLOCSET_DEFAULT_MINSIZE,
384+
ALLOCSET_DEFAULT_INITSIZE,
385+
ALLOCSET_DEFAULT_MAXSIZE);
386+
return context->scratch_ctx;
387+
}
388+
367389
static PLyExecutionContext *
368390
PLy_push_execution_context(void)
369391
{
370-
PLyExecutionContext *context = PLy_malloc(sizeof(PLyExecutionContext));
392+
PLyExecutionContext *context;
371393

394+
context = (PLyExecutionContext *)
395+
MemoryContextAlloc(TopTransactionContext, sizeof(PLyExecutionContext));
372396
context->curr_proc = NULL;
373-
context->scratch_ctx = AllocSetContextCreate(TopTransactionContext,
374-
"PL/Python scratch context",
375-
ALLOCSET_DEFAULT_MINSIZE,
376-
ALLOCSET_DEFAULT_INITSIZE,
377-
ALLOCSET_DEFAULT_MAXSIZE);
397+
context->scratch_ctx = NULL;
378398
context->next = PLy_execution_contexts;
379399
PLy_execution_contexts = context;
380400
return context;
@@ -390,6 +410,7 @@ PLy_pop_execution_context(void)
390410

391411
PLy_execution_contexts = context->next;
392412

393-
MemoryContextDelete(context->scratch_ctx);
394-
PLy_free(context);
413+
if (context->scratch_ctx)
414+
MemoryContextDelete(context->scratch_ctx);
415+
pfree(context);
395416
}

‎src/pl/plpython/plpy_main.h

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -25,4 +25,7 @@ typedef struct PLyExecutionContext
2525
/* Get the current execution context */
2626
extern PLyExecutionContext *PLy_current_execution_context(void);
2727

28+
/* Get the scratch memory context for specified execution context */
29+
extern MemoryContext PLy_get_scratch_context(PLyExecutionContext *context);
30+
2831
#endif /* PLPY_MAIN_H */

‎src/pl/plpython/plpy_planobject.c

Lines changed: 8 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -11,6 +11,7 @@
1111
#include "plpy_planobject.h"
1212

1313
#include "plpy_elog.h"
14+
#include "utils/memutils.h"
1415

1516

1617
static void PLy_plan_dealloc(PyObject *arg);
@@ -80,6 +81,7 @@ PLy_plan_new(void)
8081
ob->types = NULL;
8182
ob->values = NULL;
8283
ob->args = NULL;
84+
ob->mcxt = NULL;
8385

8486
return (PyObject *) ob;
8587
}
@@ -96,20 +98,15 @@ PLy_plan_dealloc(PyObject *arg)
9698
PLyPlanObject *ob = (PLyPlanObject *) arg;
9799

98100
if (ob->plan)
101+
{
99102
SPI_freeplan(ob->plan);
100-
if (ob->types)
101-
PLy_free(ob->types);
102-
if (ob->values)
103-
PLy_free(ob->values);
104-
if (ob->args)
103+
ob->plan = NULL;
104+
}
105+
if (ob->mcxt)
105106
{
106-
int i;
107-
108-
for (i = 0; i < ob->nargs; i++)
109-
PLy_typeinfo_dealloc(&ob->args[i]);
110-
PLy_free(ob->args);
107+
MemoryContextDelete(ob->mcxt);
108+
ob->mcxt = NULL;
111109
}
112-
113110
arg->ob_type->tp_free(arg);
114111
}
115112

‎src/pl/plpython/plpy_planobject.h

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -17,6 +17,7 @@ typedef struct PLyPlanObject
1717
Oid *types;
1818
Datum *values;
1919
PLyTypeInfo *args;
20+
MemoryContext mcxt;
2021
} PLyPlanObject;
2122

2223
extern void PLy_plan_init_type(void);

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