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This change allows us to eliminate the previous limit on stored query length, and it makes the shared-memory hash table very much smaller, allowing more statements to be tracked. (The default value of pg_stat_statements.max is therefore increased from 1000 to 5000.) In typical scenarios, the hash table can be large enough to hold all the statements commonly issued by an application, so that there is little "churn" in the set of tracked statements, and thus little need to do I/O to the file. To further reduce the need for I/O to the query-texts file, add a way to retrieve all the columns of the pg_stat_statements view except for the query text column. This is probably not of much interest for human use but it could be exploited by programs, which will prefer using the queryid anyway. Ordinarily, we'd need to bump the extension version number for the latter change. But since we already advanced pg_stat_statements' version number from 1.1 to 1.2 in the 9.4 development cycle, it seems all right to just redefine what 1.2 means. Peter Geoghegan, reviewed by Pavel Stehule
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "gmake all" and "gmake
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.