diff options
| -rw-r--r-- | doc/src/sgml/monitoring.sgml | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index f2d99b5c117..1976f5c2967 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -3296,8 +3296,11 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i <entry><literal><function>pg_stat_get_xact_blocks_fetched</function>(oid)</literal><indexterm><primary>pg_stat_get_xact_blocks_fetched</primary></indexterm></entry> <entry><type>bigint</type></entry> <entry> - Returns the number of buffers fetched for table or index, in the current - transaction. + Returns the number of block read requests for table or index, in the + current transaction. This number minus + <function>pg_stat_get_xact_blocks_hit</function> gives the number of + kernel <function>read()</function> calls; the number of actual + physical reads is usually lower due to kernel-level buffering. </entry> </row> @@ -3305,8 +3308,9 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i <entry><literal><function>pg_stat_get_xact_blocks_hit</function>(oid)</literal><indexterm><primary>pg_stat_get_xact_blocks_hit</primary></indexterm></entry> <entry><type>bigint</type></entry> <entry> - Returns the number of buffer hits for table or index, in the current - transaction. + Returns the number of block read requests for table or index, in the + current transaction, found in cache (not triggering kernel + <function>read()</function> calls). </entry> </row> |