1 files changed, 225 insertions, 0 deletions
diff --git a/src/backend/utils/activity/pgstat_function.c b/src/backend/utils/activity/pgstat_function.c
new file mode 100644
index 00000000000..ad37bb74aa6
--- /dev/null
+++ b/src/backend/utils/activity/pgstat_function.c
@@ -0,0 +1,225 @@
+/* -------------------------------------------------------------------------
+ *
+ * pgstat_function.c
+ *	  Implementation of function statistics.
+ *
+ * This file contains the implementation of function statistics. It is kept
+ * separate from pgstat.c to enforce the line between the statistics access /
+ * storage implementation and the details about individual types of
+ * statistics.
+ *
+ * Copyright (c) 2001-2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/utils/activity/pgstat_function.c
+ * -------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "utils/pgstat_internal.h"
+#include "utils/timestamp.h"
+
+
+/* ----------
+ * GUC parameters
+ * ----------
+ */
+int			pgstat_track_functions = TRACK_FUNC_OFF;
+
+
+/*
+ * Indicates if backend has some function stats that it hasn't yet
+ * sent to the collector.
+ */
+bool		have_function_stats = false;
+
+/*
+ * Backends store per-function info that's waiting to be sent to the collector
+ * in this hash table (indexed by function OID).
+ */
+static HTAB *pgStatFunctions = NULL;
+
+/*
+ * Total time charged to functions so far in the current backend.
+ * We use this to help separate "self" and "other" time charges.
+ * (We assume this initializes to zero.)
+ */
+static instr_time total_func_time;
+
+
+/*
+ * Initialize function call usage data.
+ * Called by the executor before invoking a function.
+ */
+void
+pgstat_init_function_usage(FunctionCallInfo fcinfo,
+						   PgStat_FunctionCallUsage *fcu)
+{
+	PgStat_BackendFunctionEntry *htabent;
+	bool		found;
+
+	if (pgstat_track_functions <= fcinfo->flinfo->fn_stats)
+	{
+		/* stats not wanted */
+		fcu->fs = NULL;
+		return;
+	}
+
+	if (!pgStatFunctions)
+	{
+		/* First time through - initialize function stat table */
+		HASHCTL		hash_ctl;
+
+		hash_ctl.keysize = sizeof(Oid);
+		hash_ctl.entrysize = sizeof(PgStat_BackendFunctionEntry);
+		pgStatFunctions = hash_create("Function stat entries",
+									  PGSTAT_FUNCTION_HASH_SIZE,
+									  &hash_ctl,
+									  HASH_ELEM | HASH_BLOBS);
+	}
+
+	/* Get the stats entry for this function, create if necessary */
+	htabent = hash_search(pgStatFunctions, &fcinfo->flinfo->fn_oid,
+						  HASH_ENTER, &found);
+	if (!found)
+		MemSet(&htabent->f_counts, 0, sizeof(PgStat_FunctionCounts));
+
+	fcu->fs = &htabent->f_counts;
+
+	/* save stats for this function, later used to compensate for recursion */
+	fcu->save_f_total_time = htabent->f_counts.f_total_time;
+
+	/* save current backend-wide total time */
+	fcu->save_total = total_func_time;
+
+	/* get clock time as of function start */
+	INSTR_TIME_SET_CURRENT(fcu->f_start);
+}
+
+/*
+ * Calculate function call usage and update stat counters.
+ * Called by the executor after invoking a function.
+ *
+ * In the case of a set-returning function that runs in value-per-call mode,
+ * we will see multiple pgstat_init_function_usage/pgstat_end_function_usage
+ * calls for what the user considers a single call of the function.  The
+ * finalize flag should be TRUE on the last call.
+ */
+void
+pgstat_end_function_usage(PgStat_FunctionCallUsage *fcu, bool finalize)
+{
+	PgStat_FunctionCounts *fs = fcu->fs;
+	instr_time	f_total;
+	instr_time	f_others;
+	instr_time	f_self;
+
+	/* stats not wanted? */
+	if (fs == NULL)
+		return;
+
+	/* total elapsed time in this function call */
+	INSTR_TIME_SET_CURRENT(f_total);
+	INSTR_TIME_SUBTRACT(f_total, fcu->f_start);
+
+	/* self usage: elapsed minus anything already charged to other calls */
+	f_others = total_func_time;
+	INSTR_TIME_SUBTRACT(f_others, fcu->save_total);
+	f_self = f_total;
+	INSTR_TIME_SUBTRACT(f_self, f_others);
+
+	/* update backend-wide total time */
+	INSTR_TIME_ADD(total_func_time, f_self);
+
+	/*
+	 * Compute the new f_total_time as the total elapsed time added to the
+	 * pre-call value of f_total_time.  This is necessary to avoid
+	 * double-counting any time taken by recursive calls of myself.  (We do
+	 * not need any similar kluge for self time, since that already excludes
+	 * any recursive calls.)
+	 */
+	INSTR_TIME_ADD(f_total, fcu->save_f_total_time);
+
+	/* update counters in function stats table */
+	if (finalize)
+		fs->f_numcalls++;
+	fs->f_total_time = f_total;
+	INSTR_TIME_ADD(fs->f_self_time, f_self);
+
+	/* indicate that we have something to send */
+	have_function_stats = true;
+}
+
+/*
+ * Subroutine for pgstat_report_stat: populate and send a function stat message
+ */
+void
+pgstat_send_funcstats(void)
+{
+	/* we assume this inits to all zeroes: */
+	static const PgStat_FunctionCounts all_zeroes;
+
+	PgStat_MsgFuncstat msg;
+	PgStat_BackendFunctionEntry *entry;
+	HASH_SEQ_STATUS fstat;
+
+	if (pgStatFunctions == NULL)
+		return;
+
+	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_FUNCSTAT);
+	msg.m_databaseid = MyDatabaseId;
+	msg.m_nentries = 0;
+
+	hash_seq_init(&fstat, pgStatFunctions);
+	while ((entry = (PgStat_BackendFunctionEntry *) hash_seq_search(&fstat)) != NULL)
+	{
+		PgStat_FunctionEntry *m_ent;
+
+		/* Skip it if no counts accumulated since last time */
+		if (memcmp(&entry->f_counts, &all_zeroes,
+				   sizeof(PgStat_FunctionCounts)) == 0)
+			continue;
+
+		/* need to convert format of time accumulators */
+		m_ent = &msg.m_entry[msg.m_nentries];
+		m_ent->f_id = entry->f_id;
+		m_ent->f_numcalls = entry->f_counts.f_numcalls;
+		m_ent->f_total_time = INSTR_TIME_GET_MICROSEC(entry->f_counts.f_total_time);
+		m_ent->f_self_time = INSTR_TIME_GET_MICROSEC(entry->f_counts.f_self_time);
+
+		if (++msg.m_nentries >= PGSTAT_NUM_FUNCENTRIES)
+		{
+			pgstat_send(&msg, offsetof(PgStat_MsgFuncstat, m_entry[0]) +
+						msg.m_nentries * sizeof(PgStat_FunctionEntry));
+			msg.m_nentries = 0;
+		}
+
+		/* reset the entry's counts */
+		MemSet(&entry->f_counts, 0, sizeof(PgStat_FunctionCounts));
+	}
+
+	if (msg.m_nentries > 0)
+		pgstat_send(&msg, offsetof(PgStat_MsgFuncstat, m_entry[0]) +
+					msg.m_nentries * sizeof(PgStat_FunctionEntry));
+
+	have_function_stats = false;
+}
+
+/*
+ * find_funcstat_entry - find any existing PgStat_BackendFunctionEntry entry
+ *		for specified function
+ *
+ * If no entry, return NULL, don't create a new one
+ */
+PgStat_BackendFunctionEntry *
+find_funcstat_entry(Oid func_id)
+{
+	pgstat_assert_is_up();
+
+	if (pgStatFunctions == NULL)
+		return NULL;
+
+	return (PgStat_BackendFunctionEntry *) hash_search(pgStatFunctions,
+													   (void *) &func_id,
+													   HASH_FIND, NULL);
+}