Add --aggregate-interval option.

The new option specifies length of aggregation interval (in
seconds). May be used only together with -l. With this option, the log
contains per-interval summary (number of transactions, min/max latency
and two additional fields useful for variance estimation).

Patch contributed by Tomas Vondra, reviewed by Pavel Stehule. Slight
change by Tatsuo Ishii, suggested by Robert Hass to emit an error
message indicating that the option is not currently supported on
Windows.

1 files changed, 57 insertions, 2 deletions

diff --git a/doc/src/sgml/pgbench.sgml b/doc/src/sgml/pgbench.sgml
index 9ed8b76963c..79b4baffbf8 100644
--- a/doc/src/sgml/pgbench.sgml
+++ b/doc/src/sgml/pgbench.sgml
@@ -351,6 +351,21 @@ pgbench <optional> <replaceable>options</> </optional> <replaceable>dbname</>
      </varlistentry>
 
      <varlistentry>
+      <term><option>--aggregate-interval</option> <replaceable>seconds</></term>
+      <listitem>
+       <para>
+        Length of aggregation interval (in seconds). May be used only together
+        with <application>-l</application> - with this option, the log contains
+        per-interval summary (number of transactions, min/max latency and two
+        additional fields useful for variance estimation).
+       </para>
+       <para>
+        This option is not currently supported on Windows.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><option>-M</option> <replaceable>querymode</></term>
       <listitem>
        <para>
@@ -746,8 +761,9 @@ END;
   <title>Per-Transaction Logging</title>
 
   <para>
-   With the <option>-l</> option, <application>pgbench</> writes the time
-   taken by each transaction to a log file.  The log file will be named
+   With the <option>-l</> option but without the <option>--aggregate-interval</option>,
+   <application>pgbench</> writes the time taken by each transaction
+   to a log file.  The log file will be named
    <filename>pgbench_log.<replaceable>nnn</></filename>, where
    <replaceable>nnn</> is the PID of the pgbench process.
    If the <option>-j</> option is 2 or higher, creating multiple worker
@@ -793,6 +809,45 @@ END;
  </refsect2>
 
  <refsect2>
+  <title>Aggregated Logging</title>
+  
+  <para>
+   With the <option>--aggregate-interval</option> option, the logs use a bit different format:
+
+<synopsis>
+<replaceable>interval_start</> <replaceable>num_of_transactions</> <replaceable>latency_sum</> <replaceable>latency_2_sum</> <replaceable>min_latency</> <replaceable>max_latency</>
+</synopsis>
+
+   where <replaceable>interval_start</> is the start of the interval (UNIX epoch
+   format timestamp), <replaceable>num_of_transactions</> is the number of transactions
+   within the interval, <replaceable>latency_sum</replaceable> is a sum of latencies
+   (so you can compute average latency easily). The following two fields are useful
+   for variance estimation - <replaceable>latency_sum</> is a sum of latencies and
+   <replaceable>latency_2_sum</> is a sum of 2nd powers of latencies. The last two
+   fields are <replaceable>min_latency</> - a minimum latency within the interval, and
+   <replaceable>max_latency</> - maximum latency within the interval. A transaction is
+   counted into the interval when it was committed.
+  </para>
+
+  <para>
+   Here is example outputs:
+<screen>
+1345828501 5601 1542744 483552416 61 2573
+1345828503 7884 1979812 565806736 60 1479
+1345828505 7208 1979422 567277552 59 1391
+1345828507 7685 1980268 569784714 60 1398
+1345828509 7073 1979779 573489941 236 1411
+</screen></para>
+
+  <para>
+   Notice that while the plain (unaggregated) log file contains index
+   of the custom script files, the aggregated log does not. Therefore if
+   you need per script data, you need to aggregate the data on your own.
+  </para>
+
+ </refsect2>
+
+ <refsect2>
   <title>Per-Statement Latencies</title>
 
   <para>