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Prior to this patch, every FETCH call would generate a unique queryId with a different size specified. Depending on the workloads, this could lead to a significant bloat in pg_stat_statements, as repeatedly calling a specific cursor would result in a new queryId each time. For example, FETCH 1 c1; and FETCH 2 c1; would produce different queryIds. This patch improves the situation by normalizing the fetch size, so as semantically similar statements generate the same queryId. As a result, statements like the below, which differ syntactically but have the same effect, will now share a single queryId: FETCH FROM c1 FETCH NEXT c1 FETCH 1 c1 In order to do a normalization based on the keyword used in FETCH, FetchStmt is tweaked with a new FetchDirectionKeywords. This matters for "howMany", which could be set to a negative value depending on the direction, and we want to normalize the queries with enough information about the direction keywords provided, including RELATIVE, ABSOLUTE or all the ALL variants. Author: Sami Imseih <samimseih@gmail.com> Discussion: https://postgr.es/m/CAA5RZ0tA6LbHCg2qSS+KuM850BZC_+ZgHV7Ug6BXw22TNyF+MA@mail.gmail.com
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 "make all" and "make
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.