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vbwagnervbwagner
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Merge branch 'PGPROEE9_6_wait_sampling' into PGPROEE9_6
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‎contrib/Makefile

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@@ -43,6 +43,7 @@ SUBDIRS = \
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pgrowlocks \
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pgstattuple \
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pg_visibility \
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pg_wait_sampling \
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postgres_fdw \
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rum \
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seg \

‎contrib/pg_wait_sampling/.gitignore

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.deps
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*.o
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*.so

‎contrib/pg_wait_sampling/Makefile

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# contrib/pg_wait_sampling/Makefile
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MODULE_big = pg_wait_sampling
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OBJS = pg_wait_sampling.o collector.o
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EXTENSION = pg_wait_sampling
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DATA = pg_wait_sampling--1.0.sql
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REGRESS = load
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EXTRA_REGRESS_OPTS=--temp-config=$(top_srcdir)/$(subdir)/conf.add
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ifdef USE_PGXS
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PG_CONFIG = pg_config
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PGXS := $(shell $(PG_CONFIG) --pgxs)
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include $(PGXS)
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else
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subdir = contrib/pg_wait_sampling
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top_builddir = ../..
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include $(top_builddir)/src/Makefile.global
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include $(top_srcdir)/contrib/contrib-global.mk
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endif

‎contrib/pg_wait_sampling/README.md

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pg\_wait\_sampling – sampling based statistics of wait events
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=============================================================
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Introduction
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------------
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PostgreSQL 9.6+ provides an information about current wait event of particular
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process. However, in order to gather descriptive statistics of server
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behavior user have to sample current wait event multiple times.
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pg\_wait\_sampling is an extension for collecting sampling statistics of wait
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events.
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The module must be loaded by adding pg\_wait\_sampling to
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shared\_preload\_libraries in postgresql.conf, because it requires additional
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shared memory and launches background worker. This means that a server restart
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is needed to add or remove the module.
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When pg\_wait\_sampling is enabled, it collects two kinds of statistics.
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* History of waits events. It's implemented as in-memory ring buffer where
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samples of each process wait events are written with given (configurable)
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period. Therefore, for each running process user can see some number of
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recent samples depending on history size (configurable). Assuming there is
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a client who periodically read this history and dump it somewhere, user
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can have continuous history.
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* Waits profile. It's implemented as in-memory hash table where count
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of samples are accumulated per each process and each wait event. This hash
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table can be reset by user request. Assuming there is a client who
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periodically dumps profile and resets it, user can have statistics of
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intensivity of wait events among time.
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pg\_wait\_sampling launches special background worker for gathering the
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statistics above.
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Authors
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-------
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* Alexander Korotkov <a.korotkov@postgrespro.ru>, Postgres Professional,
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Moscow, Russia
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Availability
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------------
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pg\_wait\_sampling is realized as an extension and not available in default
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PostgreSQL installation. It is available from
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[github](https://github.com/postgrespro/pg_wait_sampling)
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under the same license as
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[PostgreSQL](http://www.postgresql.org/about/licence/)
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and supports PostgreSQL 9.6+.
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Installation
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------------
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pg\_wait\_sampling is PostgreSQL extension which requires PostgreSQL 9.6 or
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higher. Before build and install you should ensure following:
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* PostgreSQL version is 9.6 or higher.
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* You have development package of PostgreSQL installed or you built
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PostgreSQL from source.
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* Your PATH variable is configured so that pg\_config command available, or
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set PG_CONFIG variable.
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Typical installation procedure may look like this:
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$ git clone https://github.com/postgrespro/pg_wait_sampling.git
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$ cd pg_wait_sampling
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$ make USE_PGXS=1
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$ sudo make USE_PGXS=1 install
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$ make USE_PGXS=1 installcheck
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$ psql DB -c "CREATE EXTENSION pg_wait_sampling;"
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Usage
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-----
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pg\_wait\_sampling interacts with user by set of views and functions.
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pg\_wait\_sampling\_current view – information about current wait events for
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all processed including background workers.
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| Column name | Column type | Description |
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| ----------- | ----------- | ----------------------- |
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| pid | int4 | Id of process |
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| event_type | text | Name of wait event type |
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| event | text | Name of wait event |
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pg_wait_sampling_get_current(pid int4) returns the same table for single given
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process.
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pg\_wait\_sampling\_history view – history of wait events obtained by sampling into
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in-memory ring buffer.
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| Column name | Column type | Description |
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| ----------- | ----------- | ----------------------- |
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| pid | int4 | Id of process |
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| ts | timestamptz | Sample timestamp |
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| event_type | text | Name of wait event type |
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| event | text | Name of wait event |
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pg\_wait\_sampling\_profile view – profile of wait events obtained by sampling into
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in-memory hash table.
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| Column name | Column type | Description |
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| ----------- | ----------- | ----------------------- |
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| pid | int4 | Id of process |
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| event_type | text | Name of wait event type |
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| event | text | Name of wait event |
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| count | text | Count of samples |
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pg_wait_sampling_reset_profile() function resets the profile.
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The work of wait event statistics collector worker is controlled by following
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GUCs.
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| Parameter name | Data type | Description | Default value |
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| ------------------------------- | --------- | ------------------------------------------- | ------------: |
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| pg_wait_sampling.history_size | int4 | Size of history in-memory ring buffer | 5000 |
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| pg_wait_sampling.history_period | int4 | Period for history sampling in milliseconds | 10 |
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| pg_wait_sampling.profile_period | int4 | Period for profile sampling in milliseconds | 10 |
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| pg_wait_sampling.profile_pid | bool | Whether profile should be per pid | true |
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If pg\_wait\_sampling.profile\_pid is set to false, sampling profile wouldn't be
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collected in per-process manner. In this case the value of pid could would
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be always zero and corresponding row contain samples among all the processes.
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These GUCs are allowed to be changed by superuser. Also, they are placed into
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shared memory. Thus, they could be changed from any backend and affects worker
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runtime.
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See
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[PostgreSQL documentation](http://www.postgresql.org/docs/devel/static/monitoring-stats.html#WAIT-EVENT-TABLE)
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for list of possible wait events.
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Contribution
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------------
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Please, notice, that pg\_wait\_sampling is still under development and while
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it's stable and tested, it may contains some bugs. Don't hesitate to raise
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[issues at github](https://github.com/postgrespro/pg_wait_sampling/issues) with
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your bug reports.
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If you're lacking of some functionality in pg\_wait\_sampling and feeling power
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to implement it then you're welcome to make pull requests.
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