On Sun, May 4, 2014 at 6:49 AM, Andres Freund <and...@2ndquadrant.com> wrote:
> +      <listitem>
> +       <para>
> +        Have pg_stat_statements use a flat file for query text storage, 
> allowing higher limits (Peter Geoghegan)
> +       </para>
> +
> +       <para>
> +        Also add the ability to retrieve all pg_stat_statements information 
> except the query text.  This allows programs to reuse the query
> +        text already retrieved by referencing queryid.
> +       </para>
> +      </listitem>
> This isn't an optional thing, is it?

This is intended to be used by time-series monitoring tools that
aggregate and graph pg_stat_statements data temporally. They usually
won't need query texts, and so can only retrieve them lazily. The
pg_stat_statements view presents exactly the same interface for ad-hoc
querying, though.

The point of the first item is that there is no longer *any*
limitation on the size of stored query texts. They are no longer
truncated to track_activity_query_size bytes. The shared memory
overhead is also decreased substantially, allowing us to increase the
default pg_stat_statements.max setting from 1,000 to 5,000, while
still reducing the overall shared memory overhead (assuming a default
track_activity_query_size). I think that the removal of the
limitation, and the substantial lowering of the per-entry footprint
should both be explicitly noted.

Peter Geoghegan

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