Make EXPLAIN (BUFFERS) track blocks dirtied, as well as those written.

Also expose the new counters through pg_stat_statements.

Patch by me.  Review by Fujii Masao and Greg Smith.

1 files changed, 19 insertions, 2 deletions

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 434aa71a33c..914fbf270d7 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -77,9 +77,11 @@ typedef struct Counters
 	int64		rows;			/* total # of retrieved or affected rows */
 	int64		shared_blks_hit;	/* # of shared buffer hits */
 	int64		shared_blks_read;		/* # of shared disk blocks read */
+	int64		shared_blks_dirtied;	/* # of shared disk blocks dirtied */
 	int64		shared_blks_written;	/* # of shared disk blocks written */
 	int64		local_blks_hit; /* # of local buffer hits */
 	int64		local_blks_read;	/* # of local disk blocks read */
+	int64		local_blks_dirtied;		/* # of local disk blocks dirtied */
 	int64		local_blks_written;		/* # of local disk blocks written */
 	int64		temp_blks_read; /* # of temp blocks read */
 	int64		temp_blks_written;		/* # of temp blocks written */
@@ -652,12 +654,16 @@ pgss_ProcessUtility(Node *parsetree, const char *queryString,
 			pgBufferUsage.shared_blks_hit - bufusage.shared_blks_hit;
 		bufusage.shared_blks_read =
 			pgBufferUsage.shared_blks_read - bufusage.shared_blks_read;
+		bufusage.shared_blks_dirtied =
+			pgBufferUsage.shared_blks_dirtied - bufusage.shared_blks_dirtied;
 		bufusage.shared_blks_written =
 			pgBufferUsage.shared_blks_written - bufusage.shared_blks_written;
 		bufusage.local_blks_hit =
 			pgBufferUsage.local_blks_hit - bufusage.local_blks_hit;
 		bufusage.local_blks_read =
 			pgBufferUsage.local_blks_read - bufusage.local_blks_read;
+		bufusage.local_blks_dirtied =
+			pgBufferUsage.local_blks_dirtied - bufusage.local_blks_dirtied;
 		bufusage.local_blks_written =
 			pgBufferUsage.local_blks_written - bufusage.local_blks_written;
 		bufusage.temp_blks_read =
@@ -766,9 +772,11 @@ pgss_store(const char *query, double total_time, uint64 rows,
 		e->counters.rows += rows;
 		e->counters.shared_blks_hit += bufusage->shared_blks_hit;
 		e->counters.shared_blks_read += bufusage->shared_blks_read;
+		e->counters.shared_blks_dirtied += bufusage->shared_blks_dirtied;
 		e->counters.shared_blks_written += bufusage->shared_blks_written;
 		e->counters.local_blks_hit += bufusage->local_blks_hit;
 		e->counters.local_blks_read += bufusage->local_blks_read;
+		e->counters.local_blks_dirtied += bufusage->local_blks_dirtied;
 		e->counters.local_blks_written += bufusage->local_blks_written;
 		e->counters.temp_blks_read += bufusage->temp_blks_read;
 		e->counters.temp_blks_written += bufusage->temp_blks_written;
@@ -793,7 +801,8 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
 	PG_RETURN_VOID();
 }
 
-#define PG_STAT_STATEMENTS_COLS		14
+#define PG_STAT_STATEMENTS_COLS_V1_0	14
+#define PG_STAT_STATEMENTS_COLS			16
 
 /*
  * Retrieve statement statistics.
@@ -810,6 +819,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 	bool		is_superuser = superuser();
 	HASH_SEQ_STATUS hash_seq;
 	pgssEntry  *entry;
+	bool		sql_supports_dirty_counters = true;
 
 	if (!pgss || !pgss_hash)
 		ereport(ERROR,
@@ -830,6 +840,8 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 	/* 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");
+	if (tupdesc->natts == PG_STAT_STATEMENTS_COLS_V1_0)
+		sql_supports_dirty_counters = false;
 
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
@@ -887,14 +899,19 @@ pg_stat_statements(PG_FUNCTION_ARGS)
 		values[i++] = Int64GetDatumFast(tmp.rows);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
+		if (sql_supports_dirty_counters)
+			values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied);
 		values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_read);
+		if (sql_supports_dirty_counters)
+			values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied);
 		values[i++] = Int64GetDatumFast(tmp.local_blks_written);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
 		values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
 
-		Assert(i == PG_STAT_STATEMENTS_COLS);
+		Assert(i == sql_supports_dirty_counters ? \
+			PG_STAT_STATEMENTS_COLS : PG_STAT_STATEMENTS_COLS_V1_0);
 
 		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
 	}