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Fix broken logic for reporting PL/Python function names in errcontext.
plpython_error_callback() reported the name of the function associated with the topmost PL/Python execution context. This was not merely wrong if there were nested PL/Python contexts, but it risked a core dump if the topmost one is an inline code block rather than a named function. That will have proname = NULL, and so we were passing a NULL pointer to snprintf("%s"). It seems that none of the PL/Python-testing machines in the buildfarm will dump core for that, but some platforms do, as reported by Marina Polyakova. Investigation finds that there actually is an existing regression test that used to prove that the behavior was wrong, though apparently no one had noticed that it was printing the wrong function name. It stopped showing the problem in 9.6 when we adjusted psql to not print CONTEXT by default for NOTICE messages. The problem is masked (if your platform avoids the core dump) in error cases, because PL/Python will throw away the originally generated error info in favor of a new traceback produced at the outer level. Repair by using ErrorContextCallback.arg to pass the correct context to the error callback. Add a regression test illustrating correct behavior. Back-patch to all supported branches, since they're all broken this way. Discussion: https://postgr.es/m/156b989dbc6fe7c4d3223cf51da61195@postgrespro.ru
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‎src/pl/plpython/expected/plpython_error.out

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -422,3 +422,26 @@ EXCEPTION WHEN SQLSTATE 'SILLY' THEN
422422
-- NOOP
423423
END
424424
$$ LANGUAGE plpgsql;
425+
/* test the context stack trace for nested execution levels
426+
*/
427+
CREATE FUNCTION notice_innerfunc() RETURNS int AS $$
428+
plpy.execute("DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$")
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return 1
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$$ LANGUAGE plpythonu;
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CREATE FUNCTION notice_outerfunc() RETURNS int AS $$
432+
plpy.execute("SELECT notice_innerfunc()")
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return 1
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$$ LANGUAGE plpythonu;
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\set SHOW_CONTEXT always
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SELECT notice_outerfunc();
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NOTICE: inside DO
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CONTEXT: PL/Python anonymous code block
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SQL statement "DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$"
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PL/Python function "notice_innerfunc"
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SQL statement "SELECT notice_innerfunc()"
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PL/Python function "notice_outerfunc"
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notice_outerfunc
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------------------
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1
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(1 row)
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‎src/pl/plpython/expected/plpython_error_0.out

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -422,3 +422,26 @@ EXCEPTION WHEN SQLSTATE 'SILLY' THEN
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-- NOOP
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END
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$$ LANGUAGE plpgsql;
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/* test the context stack trace for nested execution levels
426+
*/
427+
CREATE FUNCTION notice_innerfunc() RETURNS int AS $$
428+
plpy.execute("DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$")
429+
return 1
430+
$$ LANGUAGE plpythonu;
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CREATE FUNCTION notice_outerfunc() RETURNS int AS $$
432+
plpy.execute("SELECT notice_innerfunc()")
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return 1
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$$ LANGUAGE plpythonu;
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\set SHOW_CONTEXT always
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SELECT notice_outerfunc();
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NOTICE: inside DO
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CONTEXT: PL/Python anonymous code block
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SQL statement "DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$"
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PL/Python function "notice_innerfunc"
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SQL statement "SELECT notice_innerfunc()"
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PL/Python function "notice_outerfunc"
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notice_outerfunc
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------------------
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1
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(1 row)
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‎src/pl/plpython/expected/plpython_error_5.out

Lines changed: 23 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -422,3 +422,26 @@ EXCEPTION WHEN SQLSTATE 'SILLY' THEN
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-- NOOP
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END
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$$ LANGUAGE plpgsql;
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/* test the context stack trace for nested execution levels
426+
*/
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CREATE FUNCTION notice_innerfunc() RETURNS int AS $$
428+
plpy.execute("DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$")
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return 1
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$$ LANGUAGE plpythonu;
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CREATE FUNCTION notice_outerfunc() RETURNS int AS $$
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plpy.execute("SELECT notice_innerfunc()")
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return 1
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$$ LANGUAGE plpythonu;
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\set SHOW_CONTEXT always
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SELECT notice_outerfunc();
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NOTICE: inside DO
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CONTEXT: PL/Python anonymous code block
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SQL statement "DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$"
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PL/Python function "notice_innerfunc"
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SQL statement "SELECT notice_innerfunc()"
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PL/Python function "notice_outerfunc"
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notice_outerfunc
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------------------
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1
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(1 row)
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‎src/pl/plpython/plpy_main.c

Lines changed: 26 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -237,23 +237,26 @@ plpython_call_handler(PG_FUNCTION_ARGS)
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/*
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* Push execution context onto stack. It is important that this get
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* popped again, so avoid putting anything that could throw error between
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* here and the PG_TRY. (plpython_error_callback expects the stack entry
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* to be there, so we have to make the context first.)
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* here and the PG_TRY.
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*/
243242
exec_ctx = PLy_push_execution_context(!nonatomic);
244243

245-
/*
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* Setup error traceback support for ereport()
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*/
248-
plerrcontext.callback = plpython_error_callback;
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plerrcontext.previous = error_context_stack;
250-
error_context_stack = &plerrcontext;
251-
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PG_TRY();
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{
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Oid funcoid = fcinfo->flinfo->fn_oid;
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PLyProcedure *proc;
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249+
/*
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* Setup error traceback support for ereport(). Note that the PG_TRY
251+
* structure pops this for us again at exit, so we needn't do that
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* explicitly, nor do we risk the callback getting called after we've
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* destroyed the exec_ctx.
254+
*/
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plerrcontext.callback = plpython_error_callback;
256+
plerrcontext.arg = exec_ctx;
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plerrcontext.previous = error_context_stack;
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error_context_stack = &plerrcontext;
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257260
if (CALLED_AS_TRIGGER(fcinfo))
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{
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Relation tgrel = ((TriggerData *) fcinfo->context)->tg_relation;
@@ -279,9 +282,7 @@ plpython_call_handler(PG_FUNCTION_ARGS)
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}
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PG_END_TRY();
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282-
/* Pop the error context stack */
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error_context_stack = plerrcontext.previous;
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/* ... and then the execution context */
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/* Destroy the execution context */
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PLy_pop_execution_context();
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return retval;
@@ -333,21 +334,22 @@ plpython_inline_handler(PG_FUNCTION_ARGS)
333334
/*
334335
* Push execution context onto stack. It is important that this get
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* popped again, so avoid putting anything that could throw error between
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* here and the PG_TRY. (plpython_inline_error_callback doesn't currently
337-
* need the stack entry, but for consistency with plpython_call_handler we
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* do it in this order.)
337+
* here and the PG_TRY.
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*/
340339
exec_ctx = PLy_push_execution_context(codeblock->atomic);
341340

342-
/*
343-
* Setup error traceback support for ereport()
344-
*/
345-
plerrcontext.callback = plpython_inline_error_callback;
346-
plerrcontext.previous = error_context_stack;
347-
error_context_stack = &plerrcontext;
348-
349341
PG_TRY();
350342
{
343+
/*
344+
* Setup error traceback support for ereport().
345+
* plpython_inline_error_callback doesn't currently need exec_ctx, but
346+
* for consistency with plpython_call_handler we do it the same way.
347+
*/
348+
plerrcontext.callback = plpython_inline_error_callback;
349+
plerrcontext.arg = exec_ctx;
350+
plerrcontext.previous = error_context_stack;
351+
error_context_stack = &plerrcontext;
352+
351353
PLy_procedure_compile(&proc, codeblock->source_text);
352354
exec_ctx->curr_proc = &proc;
353355
PLy_exec_function(&fake_fcinfo, &proc);
@@ -361,9 +363,7 @@ plpython_inline_handler(PG_FUNCTION_ARGS)
361363
}
362364
PG_END_TRY();
363365

364-
/* Pop the error context stack */
365-
error_context_stack = plerrcontext.previous;
366-
/* ... and then the execution context */
366+
/* Destroy the execution context */
367367
PLy_pop_execution_context();
368368

369369
/* Now clean up the transient procedure we made */
@@ -391,7 +391,7 @@ PLy_procedure_is_trigger(Form_pg_proc procStruct)
391391
static void
392392
plpython_error_callback(void *arg)
393393
{
394-
PLyExecutionContext *exec_ctx = PLy_current_execution_context();
394+
PLyExecutionContext *exec_ctx = (PLyExecutionContext *) arg;
395395

396396
if (exec_ctx->curr_proc)
397397
{

‎src/pl/plpython/plpy_procedure.c

Lines changed: 1 addition & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -47,9 +47,7 @@ init_procedure_caches(void)
4747
}
4848

4949
/*
50-
* Get the name of the last procedure called by the backend (the
51-
* innermost, if a plpython procedure call calls the backend and the
52-
* backend calls another plpython procedure).
50+
* PLy_procedure_name: get the name of the specified procedure.
5351
*
5452
* NB: this returns the SQL name, not the internal Python procedure name
5553
*/

‎src/pl/plpython/sql/plpython_error.sql

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -328,3 +328,19 @@ EXCEPTION WHEN SQLSTATE 'SILLY' THEN
328328
-- NOOP
329329
END
330330
$$ LANGUAGE plpgsql;
331+
332+
/* test the context stack trace for nested execution levels
333+
*/
334+
CREATE FUNCTION notice_innerfunc() RETURNS int AS $$
335+
plpy.execute("DO LANGUAGE plpythonu $x$ plpy.notice('inside DO') $x$")
336+
return 1
337+
$$ LANGUAGE plpythonu;
338+
339+
CREATE FUNCTION notice_outerfunc() RETURNS int AS $$
340+
plpy.execute("SELECT notice_innerfunc()")
341+
return 1
342+
$$ LANGUAGE plpythonu;
343+
344+
\set SHOW_CONTEXT always
345+
346+
SELECT notice_outerfunc();

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