I wrote:
> Robert Haas <robertmh...@gmail.com> writes:
>> I'm not volunteering to spend time fixing this, but I disagree with
>> the premise that it isn't worth fixing, because I think it's a POLA
>> violation.
> Yeah, I'm not terribly comfortable with letting it go either. Attached
> is a proposed patch. I couldn't see any nice way to do it without adding
> a field to PLpgSQL_execstate, so this isn't a feasible solution for
> back-patching (it'd break the plpgsql debugger). However, given the
> infrequency of complaints, I think fixing it in 9.4 and up is good enough.
This patch crashed and burned when I tried it on a case where a DO block
traps an exception :-(. I had thought that a private econtext stack was
the right thing to do, but it isn't because we need plpgsql_subxact_cb
to be able to clean up dead econtexts in either functions or DO blocks.
So after some experimentation I came up with version 2, attached.
The additional test case I was using looks like
do $outer$
begin
for i in 1..100000 loop
begin
execute $e$
do $$
declare x int = 0;
begin
x := 1 / x;
end;
$$;
$e$;
exception when division_by_zero then null;
end;
end loop;
end;
$outer$;
If you try this with the patch, you'll notice that there's still a slow
leak, but that's not the fault of DO blocks: the same leak exists if you
transpose this code into a regular function. That leak is the fault of
exec_stmt_dynexecute, which copies the querystring into the function's
main execution context, from which it won't get freed if an error is
thrown out of SPI_execute. (If we were using EXECUTE USING, the "ppd"
structure would get leaked too.) There are some other similar error-
case leaks in other plpgsql statements, I think. I'm not excited
about trying to clean those up as part of this patch.
regards, tom lane
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index bc31fe9..f5f1892 100644
*** a/src/pl/plpgsql/src/pl_exec.c
--- b/src/pl/plpgsql/src/pl_exec.c
*************** typedef struct
*** 66,71 ****
--- 66,80 ----
* so that we don't have to re-prepare simple expressions on each trip through
* a function. (We assume the case to optimize is many repetitions of a
* function within a transaction.)
+ *
+ * However, there's no value in trying to amortize simple expression setup
+ * across multiple executions of a DO block (inline code block), since there
+ * can never be any. If we use the shared EState for a DO block, the expr
+ * state trees are effectively leaked till end of transaction, and that can
+ * add up if the user keeps on submitting DO blocks. Therefore, each DO block
+ * has its own simple-expression EState, which is cleaned up at exit from
+ * plpgsql_inline_handler(). DO blocks still use the simple_econtext_stack,
+ * though, so that subxact abort cleanup does the right thing.
*/
typedef struct SimpleEcontextStackEntry
{
*************** typedef struct SimpleEcontextStackEntry
*** 74,80 ****
struct SimpleEcontextStackEntry *next; /* next stack entry up */
} SimpleEcontextStackEntry;
! static EState *simple_eval_estate = NULL;
static SimpleEcontextStackEntry *simple_econtext_stack = NULL;
/************************************************************
--- 83,89 ----
struct SimpleEcontextStackEntry *next; /* next stack entry up */
} SimpleEcontextStackEntry;
! static EState *shared_simple_eval_estate = NULL;
static SimpleEcontextStackEntry *simple_econtext_stack = NULL;
/************************************************************
*************** static int exec_stmt_dynfors(PLpgSQL_exe
*** 136,142 ****
static void plpgsql_estate_setup(PLpgSQL_execstate *estate,
PLpgSQL_function *func,
! ReturnSetInfo *rsi);
static void exec_eval_cleanup(PLpgSQL_execstate *estate);
static void exec_prepare_plan(PLpgSQL_execstate *estate,
--- 145,152 ----
static void plpgsql_estate_setup(PLpgSQL_execstate *estate,
PLpgSQL_function *func,
! ReturnSetInfo *rsi,
! EState *simple_eval_estate);
static void exec_eval_cleanup(PLpgSQL_execstate *estate);
static void exec_prepare_plan(PLpgSQL_execstate *estate,
*************** static char *format_preparedparamsdata(P
*** 230,239 ****
/* ----------
* plpgsql_exec_function Called by the call handler for
* function execution.
* ----------
*/
Datum
! plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo)
{
PLpgSQL_execstate estate;
ErrorContextCallback plerrcontext;
--- 240,256 ----
/* ----------
* plpgsql_exec_function Called by the call handler for
* function execution.
+ *
+ * This is also used to execute inline code blocks (DO blocks). The only
+ * difference that this code is aware of is that for a DO block, we want
+ * to use a private simple_eval_estate, which is created and passed in by
+ * the caller. For regular functions, pass NULL, which implies using
+ * shared_simple_eval_estate.
* ----------
*/
Datum
! plpgsql_exec_function(PLpgSQL_function *func, FunctionCallInfo fcinfo,
! EState *simple_eval_estate)
{
PLpgSQL_execstate estate;
ErrorContextCallback plerrcontext;
*************** plpgsql_exec_function(PLpgSQL_function *
*** 243,249 ****
/*
* Setup the execution state
*/
! plpgsql_estate_setup(&estate, func, (ReturnSetInfo *) fcinfo->resultinfo);
/*
* Setup error traceback support for ereport()
--- 260,267 ----
/*
* Setup the execution state
*/
! plpgsql_estate_setup(&estate, func, (ReturnSetInfo *) fcinfo->resultinfo,
! simple_eval_estate);
/*
* Setup error traceback support for ereport()
*************** plpgsql_exec_trigger(PLpgSQL_function *f
*** 503,509 ****
/*
* Setup the execution state
*/
! plpgsql_estate_setup(&estate, func, NULL);
/*
* Setup error traceback support for ereport()
--- 521,527 ----
/*
* Setup the execution state
*/
! plpgsql_estate_setup(&estate, func, NULL, NULL);
/*
* Setup error traceback support for ereport()
*************** plpgsql_exec_event_trigger(PLpgSQL_funct
*** 782,788 ****
/*
* Setup the execution state
*/
! plpgsql_estate_setup(&estate, func, NULL);
/*
* Setup error traceback support for ereport()
--- 800,806 ----
/*
* Setup the execution state
*/
! plpgsql_estate_setup(&estate, func, NULL, NULL);
/*
* Setup error traceback support for ereport()
*************** exec_stmt_raise(PLpgSQL_execstate *estat
*** 3087,3093 ****
static void
plpgsql_estate_setup(PLpgSQL_execstate *estate,
PLpgSQL_function *func,
! ReturnSetInfo *rsi)
{
/* this link will be restored at exit from plpgsql_call_handler */
func->cur_estate = estate;
--- 3105,3112 ----
static void
plpgsql_estate_setup(PLpgSQL_execstate *estate,
PLpgSQL_function *func,
! ReturnSetInfo *rsi,
! EState *simple_eval_estate)
{
/* this link will be restored at exit from plpgsql_call_handler */
func->cur_estate = estate;
*************** plpgsql_estate_setup(PLpgSQL_execstate *
*** 3126,3131 ****
--- 3145,3156 ----
estate->datums = palloc(sizeof(PLpgSQL_datum *) * estate->ndatums);
/* caller is expected to fill the datums array */
+ /* set up for use of appropriate simple-expression EState */
+ if (simple_eval_estate)
+ estate->simple_eval_estate = simple_eval_estate;
+ else
+ estate->simple_eval_estate = shared_simple_eval_estate;
+
estate->eval_tuptable = NULL;
estate->eval_processed = 0;
estate->eval_lastoid = InvalidOid;
*************** exec_eval_simple_expr(PLpgSQL_execstate
*** 5148,5154 ****
*/
if (expr->expr_simple_lxid != curlxid)
{
! oldcontext = MemoryContextSwitchTo(simple_eval_estate->es_query_cxt);
expr->expr_simple_state = ExecInitExpr(expr->expr_simple_expr, NULL);
expr->expr_simple_in_use = false;
expr->expr_simple_lxid = curlxid;
--- 5173,5179 ----
*/
if (expr->expr_simple_lxid != curlxid)
{
! oldcontext = MemoryContextSwitchTo(estate->simple_eval_estate->es_query_cxt);
expr->expr_simple_state = ExecInitExpr(expr->expr_simple_expr, NULL);
expr->expr_simple_in_use = false;
expr->expr_simple_lxid = curlxid;
*************** exec_set_found(PLpgSQL_execstate *estate
*** 6190,6197 ****
/*
* plpgsql_create_econtext --- create an eval_econtext for the current function
*
! * We may need to create a new simple_eval_estate too, if there's not one
! * already for the current transaction. The EState will be cleaned up at
* transaction end.
*/
static void
--- 6215,6222 ----
/*
* plpgsql_create_econtext --- create an eval_econtext for the current function
*
! * We may need to create a new shared_simple_eval_estate too, if there's not
! * one already for the current transaction. The EState will be cleaned up at
* transaction end.
*/
static void
*************** plpgsql_create_econtext(PLpgSQL_execstat
*** 6203,6222 ****
* Create an EState for evaluation of simple expressions, if there's not
* one already in the current transaction. The EState is made a child of
* TopTransactionContext so it will have the right lifespan.
*/
! if (simple_eval_estate == NULL)
{
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(TopTransactionContext);
! simple_eval_estate = CreateExecutorState();
MemoryContextSwitchTo(oldcontext);
}
/*
* Create a child econtext for the current function.
*/
! estate->eval_econtext = CreateExprContext(simple_eval_estate);
/*
* Make a stack entry so we can clean up the econtext at subxact end.
--- 6228,6252 ----
* Create an EState for evaluation of simple expressions, if there's not
* one already in the current transaction. The EState is made a child of
* TopTransactionContext so it will have the right lifespan.
+ *
+ * Note that this path is never taken when executing a DO block; the
+ * required EState was already made by plpgsql_inline_handler.
*/
! if (estate->simple_eval_estate == NULL)
{
MemoryContext oldcontext;
+ Assert(shared_simple_eval_estate == NULL);
oldcontext = MemoryContextSwitchTo(TopTransactionContext);
! shared_simple_eval_estate = CreateExecutorState();
! estate->simple_eval_estate = shared_simple_eval_estate;
MemoryContextSwitchTo(oldcontext);
}
/*
* Create a child econtext for the current function.
*/
! estate->eval_econtext = CreateExprContext(estate->simple_eval_estate);
/*
* Make a stack entry so we can clean up the econtext at subxact end.
*************** plpgsql_xact_cb(XactEvent event, void *a
*** 6275,6288 ****
/* Shouldn't be any econtext stack entries left at commit */
Assert(simple_econtext_stack == NULL);
! if (simple_eval_estate)
! FreeExecutorState(simple_eval_estate);
! simple_eval_estate = NULL;
}
else if (event == XACT_EVENT_ABORT)
{
simple_econtext_stack = NULL;
! simple_eval_estate = NULL;
}
}
--- 6305,6318 ----
/* Shouldn't be any econtext stack entries left at commit */
Assert(simple_econtext_stack == NULL);
! if (shared_simple_eval_estate)
! FreeExecutorState(shared_simple_eval_estate);
! shared_simple_eval_estate = NULL;
}
else if (event == XACT_EVENT_ABORT)
{
simple_econtext_stack = NULL;
! shared_simple_eval_estate = NULL;
}
}
*************** plpgsql_xact_cb(XactEvent event, void *a
*** 6291,6298 ****
*
* Make sure any simple-expression econtexts created in the current
* subtransaction get cleaned up. We have to do this explicitly because
! * no other code knows which child econtexts of simple_eval_estate belong
! * to which level of subxact.
*/
void
plpgsql_subxact_cb(SubXactEvent event, SubTransactionId mySubid,
--- 6321,6327 ----
*
* Make sure any simple-expression econtexts created in the current
* subtransaction get cleaned up. We have to do this explicitly because
! * no other code knows which econtexts belong to which level of subxact.
*/
void
plpgsql_subxact_cb(SubXactEvent event, SubTransactionId mySubid,
diff --git a/src/pl/plpgsql/src/pl_handler.c b/src/pl/plpgsql/src/pl_handler.c
index 912422c..5bfe3c3 100644
*** a/src/pl/plpgsql/src/pl_handler.c
--- b/src/pl/plpgsql/src/pl_handler.c
*************** plpgsql_call_handler(PG_FUNCTION_ARGS)
*** 136,142 ****
retval = (Datum) 0;
}
else
! retval = plpgsql_exec_function(func, fcinfo);
}
PG_CATCH();
{
--- 136,142 ----
retval = (Datum) 0;
}
else
! retval = plpgsql_exec_function(func, fcinfo, NULL);
}
PG_CATCH();
{
*************** plpgsql_inline_handler(PG_FUNCTION_ARGS)
*** 175,180 ****
--- 175,181 ----
PLpgSQL_function *func;
FunctionCallInfoData fake_fcinfo;
FmgrInfo flinfo;
+ EState *simple_eval_estate;
Datum retval;
int rc;
*************** plpgsql_inline_handler(PG_FUNCTION_ARGS)
*** 203,209 ****
flinfo.fn_oid = InvalidOid;
flinfo.fn_mcxt = CurrentMemoryContext;
! retval = plpgsql_exec_function(func, &fake_fcinfo);
/* Function should now have no remaining use-counts ... */
func->use_count--;
--- 204,254 ----
flinfo.fn_oid = InvalidOid;
flinfo.fn_mcxt = CurrentMemoryContext;
! /* Create a private EState for simple-expression execution */
! simple_eval_estate = CreateExecutorState();
!
! /* And run the function */
! PG_TRY();
! {
! retval = plpgsql_exec_function(func, &fake_fcinfo, simple_eval_estate);
! }
! PG_CATCH();
! {
! /*
! * We need to clean up what would otherwise be long-lived resources
! * accumulated by the failed DO block, principally cached plans for
! * statements (which can be flushed with plpgsql_free_function_memory)
! * and execution trees for simple expressions, which are in the
! * private EState.
! *
! * Before releasing the private EState, we must clean up any
! * simple_econtext_stack entries pointing into it, which we can do by
! * invoking the subxact callback. (It will be called again later if
! * some outer control level does a subtransaction abort, but no harm
! * is done.) We cheat a bit knowing that plpgsql_subxact_cb does not
! * pay attention to its parentSubid argument.
! */
! plpgsql_subxact_cb(SUBXACT_EVENT_ABORT_SUB,
! GetCurrentSubTransactionId(),
! 0, NULL);
!
! /* Clean up the private EState */
! FreeExecutorState(simple_eval_estate);
!
! /* Function should now have no remaining use-counts ... */
! func->use_count--;
! Assert(func->use_count == 0);
!
! /* ... so we can free subsidiary storage */
! plpgsql_free_function_memory(func);
!
! /* And propagate the error */
! PG_RE_THROW();
! }
! PG_END_TRY();
!
! /* Clean up the private EState */
! FreeExecutorState(simple_eval_estate);
/* Function should now have no remaining use-counts ... */
func->use_count--;
diff --git a/src/pl/plpgsql/src/plpgsql.h b/src/pl/plpgsql/src/plpgsql.h
index 9cb4f53..3afcdf3 100644
*** a/src/pl/plpgsql/src/plpgsql.h
--- b/src/pl/plpgsql/src/plpgsql.h
*************** typedef struct PLpgSQL_execstate
*** 773,782 ****
--- 773,786 ----
ResourceOwner tuple_store_owner;
ReturnSetInfo *rsi;
+ /* the datums representing the function's local variables */
int found_varno;
int ndatums;
PLpgSQL_datum **datums;
+ /* EState to use for "simple" expression evaluation */
+ EState *simple_eval_estate;
+
/* temporary state for results from evaluation of query or expr */
SPITupleTable *eval_tuptable;
uint32 eval_processed;
*************** extern Datum plpgsql_validator(PG_FUNCTI
*** 943,949 ****
* ----------
*/
extern Datum plpgsql_exec_function(PLpgSQL_function *func,
! FunctionCallInfo fcinfo);
extern HeapTuple plpgsql_exec_trigger(PLpgSQL_function *func,
TriggerData *trigdata);
extern void plpgsql_exec_event_trigger(PLpgSQL_function *func,
--- 947,954 ----
* ----------
*/
extern Datum plpgsql_exec_function(PLpgSQL_function *func,
! FunctionCallInfo fcinfo,
! EState *simple_eval_estate);
extern HeapTuple plpgsql_exec_trigger(PLpgSQL_function *func,
TriggerData *trigdata);
extern void plpgsql_exec_event_trigger(PLpgSQL_function *func,
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