All, * Robert Haas (robertmh...@gmail.com) wrote (on the role attributes * thread): > I think this patch is too big and does too many things. It should be > broken up into small patches which can be discussed and validated > independently. The fact that your commit message is incredibly long > is a sign that there's too much going on here, and that message > doesn't even cover all of it.
As I mentioned on another thread, you're certainly right about that, and
here's the first broken-out patch, which just changes
pg_stat_get_activity to build and return a tuplestore in a single
function call instead of using the old-style multiple-invokation call
method. Given the simplicity and the lack of any user-visible change,
and that it's an independently useful change regardless of what happens
with the other changes, I'm planning to move forward with this pretty
quickly, barring concerns, of course.
This is heavily based on the pg_stat_get_wal_senders() implementation,
hat-tip to Itagaki Takahiro for that.
Thanks!
Stephen
From d08171691f579b60e6c0652ffef886bbf0b66d85 Mon Sep 17 00:00:00 2001
From: Stephen Frost <sfr...@snowman.net>
Date: Thu, 7 May 2015 16:41:00 -0400
Subject: [PATCH] Modify pg_stat_get_activity to build a tuplestore
This updates pg_stat_get_activity() to build a tuplestore for its
results instead of using the old-style multiple-call method. This
simplifies the function, though that wasn't the primary motivation for
the change, which is that we may turn it into a helper function which
can filter the results (or not) much more easily.
---
src/backend/utils/adt/pgstatfuncs.c | 194 +++++++++++++-----------------------
1 file changed, 67 insertions(+), 127 deletions(-)
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index bbe94c3..2b3778b 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -524,137 +524,75 @@ pg_stat_get_backend_idset(PG_FUNCTION_ARGS)
}
}
+/*
+ * Returns activity of PG backends.
+ */
Datum
pg_stat_get_activity(PG_FUNCTION_ARGS)
{
- FuncCallContext *funcctx;
-
- if (SRF_IS_FIRSTCALL())
- {
- MemoryContext oldcontext;
- TupleDesc tupdesc;
-
- funcctx = SRF_FIRSTCALL_INIT();
-
- oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
-
- tupdesc = CreateTemplateTupleDesc(22, false);
- TupleDescInitEntry(tupdesc, (AttrNumber) 1, "datid",
- OIDOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 2, "pid",
- INT4OID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 3, "usesysid",
- OIDOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 4, "application_name",
- TEXTOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 5, "state",
- TEXTOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 6, "query",
- TEXTOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 7, "waiting",
- BOOLOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 8, "act_start",
- TIMESTAMPTZOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 9, "query_start",
- TIMESTAMPTZOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 10, "backend_start",
- TIMESTAMPTZOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 11, "state_change",
- TIMESTAMPTZOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 12, "client_addr",
- INETOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 13, "client_hostname",
- TEXTOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 14, "client_port",
- INT4OID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 15, "backend_xid",
- XIDOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 16, "backend_xmin",
- XIDOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 17, "ssl",
- BOOLOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 18, "sslversion",
- TEXTOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 19, "sslcipher",
- TEXTOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 20, "sslbits",
- INT4OID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 21, "sslcompression",
- BOOLOID, -1, 0);
- TupleDescInitEntry(tupdesc, (AttrNumber) 22, "sslclientdn",
- TEXTOID, -1, 0);
-
- funcctx->tuple_desc = BlessTupleDesc(tupdesc);
-
- funcctx->user_fctx = palloc0(sizeof(int));
- if (PG_ARGISNULL(0))
- {
- /* Get all backends */
- funcctx->max_calls = pgstat_fetch_stat_numbackends();
- }
- else
- {
- /*
- * Get one backend - locate by pid.
- *
- * We lookup the backend early, so we can return zero rows if it
- * doesn't exist, instead of returning a single row full of NULLs.
- */
- int pid = PG_GETARG_INT32(0);
- int i;
- int n = pgstat_fetch_stat_numbackends();
-
- for (i = 1; i <= n; i++)
- {
- PgBackendStatus *be = pgstat_fetch_stat_beentry(i);
-
- if (be)
- {
- if (be->st_procpid == pid)
- {
- *(int *) (funcctx->user_fctx) = i;
- break;
- }
- }
- }
-
- if (*(int *) (funcctx->user_fctx) == 0)
- /* Pid not found, return zero rows */
- funcctx->max_calls = 0;
- else
- funcctx->max_calls = 1;
- }
-
- MemoryContextSwitchTo(oldcontext);
- }
-
- /* stuff done on every call of the function */
- funcctx = SRF_PERCALL_SETUP();
-
- if (funcctx->call_cntr < funcctx->max_calls)
+#define PG_STAT_GET_ACTIVITY_COLS 22
+ int num_backends = pgstat_fetch_stat_numbackends();
+ int curr_backend;
+ int pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+ ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+ TupleDesc tupdesc;
+ Tuplestorestate *tupstore;
+ MemoryContext per_query_ctx;
+ MemoryContext oldcontext;
+
+ /* check to see if caller supports us returning a tuplestore */
+ if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("set-valued function called in context that cannot accept a set")));
+ if (!(rsinfo->allowedModes & SFRM_Materialize))
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("materialize mode required, but it is not " \
+ "allowed in this context")));
+
+ /* Build a tuple descriptor for our result type */
+ if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+ elog(ERROR, "return type must be a row type");
+
+ per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
+ oldcontext = MemoryContextSwitchTo(per_query_ctx);
+
+ tupstore = tuplestore_begin_heap(true, false, work_mem);
+ rsinfo->returnMode = SFRM_Materialize;
+ rsinfo->setResult = tupstore;
+ rsinfo->setDesc = tupdesc;
+
+ MemoryContextSwitchTo(oldcontext);
+
+ /* 1-based index */
+ for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
{
/* for each row */
- Datum values[22];
- bool nulls[22];
- HeapTuple tuple;
+ Datum values[PG_STAT_GET_ACTIVITY_COLS];
+ bool nulls[PG_STAT_GET_ACTIVITY_COLS];
LocalPgBackendStatus *local_beentry;
PgBackendStatus *beentry;
MemSet(values, 0, sizeof(values));
MemSet(nulls, 0, sizeof(nulls));
- if (*(int *) (funcctx->user_fctx) > 0)
- {
- /* Get specific pid slot */
- local_beentry = pgstat_fetch_stat_local_beentry(*(int *) (funcctx->user_fctx));
- beentry = &local_beentry->backendStatus;
- }
- else
+ if (pid != -1)
{
- /* Get the next one in the list */
- local_beentry = pgstat_fetch_stat_local_beentry(funcctx->call_cntr + 1); /* 1-based index */
- beentry = &local_beentry->backendStatus;
+ /* Skip any which are not the one we're looking for. */
+ PgBackendStatus *be = pgstat_fetch_stat_beentry(curr_backend);
+
+ if (!be || be->st_procpid != pid)
+ continue;
+
}
+
+ /* Get the next one in the list */
+ local_beentry = pgstat_fetch_stat_local_beentry(curr_backend);
+ if (!local_beentry)
+ continue;
+
+ beentry = &local_beentry->backendStatus;
if (!beentry)
{
int i;
@@ -665,8 +603,8 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
nulls[5] = false;
values[5] = CStringGetTextDatum("<backend information not available>");
- tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
- SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
+ tuplestore_putvalues(tupstore, tupdesc, values, nulls);
+ continue;
}
/* Values available to all callers */
@@ -839,15 +777,17 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
nulls[13] = true;
}
- tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
+ tuplestore_putvalues(tupstore, tupdesc, values, nulls);
- SRF_RETURN_NEXT(funcctx, HeapTupleGetDatum(tuple));
- }
- else
- {
- /* nothing left */
- SRF_RETURN_DONE(funcctx);
+ /* If only a single backend was requested, and we found it, break. */
+ if (pid != -1)
+ break;
}
+
+ /* clean up and return the tuplestore */
+ tuplestore_donestoring(tupstore);
+
+ return (Datum) 0;
}
--
1.9.1
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