I am managing a linux cluster which has been build on Platform Cluster Manager PCM 1.2.1) from IBM Platform Computing. Unfortunately somebody deteled data files of postgresql from /var/lib directory. I somehow managed to start the postmaster service again, but all the administrative commands of... (2 Replies)
Hi all,
I want to install two postgreql 8.3.5 instances on same servers. already one instalce is running on default port and i need it to be installed on another port.. How ever i achived installing the second instance.. but the problem is if i create a new user using createuser in the newly... (3 Replies)
I am first year year student .. and i need help
i tried to work with PostgreSQL but when i open the terminal, i face problem in how to reach to PostgreSQL . always i get message it says that " can not find server " .
so what shall i do please .....:( (9 Replies)
Hi guys.
I was was designing a simple database in postgresql. I wrote a perl function in postgresql and execute it. suddenly i saw that it is running in an infinite loop. After i stopped executing of the query, i saw that CPU is in 90%+ load. I looked at process list and there it was. postgresql... (1 Reply)
Hi guys.
I have some questions about SQL functions in postgresql:
1. Can a SQL function call another SQL function?
2. How about recursive calls?
3. Consider we have function that has a varchar argument.
CREATE FUNCTION func(varchar) RETURN void AS $$
some SQL queries.
... (0 Replies)
Guys,
I guess, I posted something in the wrong forum. Here it is -
https://www.unix.com/shell-programming-scripting/67395-perl-postgrepsql-question.html
Can you please help me with this?
Regards,
garric (0 Replies)
Hi,
I am writing a Java Swing application and want to add Embedded SQL to it. The application should interact with a PostgreSQL database running on my local machine. The compiler complains that it cannot find the org.postgresql package included in the code. I'm guessing the problem is that... (0 Replies)
ANALYZE(7) SQL Commands ANALYZE(7)NAME
ANALYZE - collect statistics about a database
SYNOPSIS
ANALYZE [ VERBOSE ] [ table [ ( column [, ...] ) ] ]
DESCRIPTION
ANALYZE collects statistics about the contents of tables in the database, and stores the results in the pg_statistic system catalog. Subse-
quently, the query planner uses these statistics to help determine the most efficient execution plans for queries.
With no parameter, ANALYZE examines every table in the current database. With a parameter, ANALYZE examines only that table. It is further
possible to give a list of column names, in which case only the statistics for those columns are collected.
PARAMETERS
VERBOSE
Enables display of progress messages.
table The name (possibly schema-qualified) of a specific table to analyze. Defaults to all tables in the current database.
column The name of a specific column to analyze. Defaults to all columns.
OUTPUTS
When VERBOSE is specified, ANALYZE emits progress messages to indicate which table is currently being processed. Various statistics about
the tables are printed as well.
NOTES
In the default PostgreSQL configuration, in the documentation takes care of automatic analyzing of tables when they are first loaded with
data, and as they change throughout regular operation. When autovacuum is disabled, it is a good idea to run ANALYZE periodically, or just
after making major changes in the contents of a table. Accurate statistics will help the planner to choose the most appropriate query plan,
and thereby improve the speed of query processing. A common strategy is to run VACUUM [vacuum(7)] and ANALYZE once a day during a low-usage
time of day.
ANALYZE requires only a read lock on the target table, so it can run in parallel with other activity on the table.
The statistics collected by ANALYZE usually include a list of some of the most common values in each column and a histogram showing the
approximate data distribution in each column. One or both of these can be omitted if ANALYZE deems them uninteresting (for example, in a
unique-key column, there are no common values) or if the column data type does not support the appropriate operators. There is more infor-
mation about the statistics in in the documentation.
For large tables, ANALYZE takes a random sample of the table contents, rather than examining every row. This allows even very large tables
to be analyzed in a small amount of time. Note, however, that the statistics are only approximate, and will change slightly each time ANA-
LYZE is run, even if the actual table contents did not change. This might result in small changes in the planner's estimated costs shown by
EXPLAIN [explain(7)]. In rare situations, this non-determinism will cause the planner's choices of query plans to change after ANALYZE is
run. To avoid this, raise the amount of statistics collected by ANALYZE, as described below.
The extent of analysis can be controlled by adjusting the default_statistics_target configuration variable, or on a column-by-column basis
by setting the per-column statistics target with ALTER TABLE ... ALTER COLUMN ... SET STATISTICS (see ALTER TABLE [alter_table(7)]). The
target value sets the maximum number of entries in the most-common-value list and the maximum number of bins in the histogram. The default
target value is 100, but this can be adjusted up or down to trade off accuracy of planner estimates against the time taken for ANALYZE and
the amount of space occupied in pg_statistic. In particular, setting the statistics target to zero disables collection of statistics for
that column. It might be useful to do that for columns that are never used as part of the WHERE, GROUP BY, or ORDER BY clauses of queries,
since the planner will have no use for statistics on such columns.
The largest statistics target among the columns being analyzed determines the number of table rows sampled to prepare the statistics.
Increasing the target causes a proportional increase in the time and space needed to do ANALYZE.
COMPATIBILITY
There is no ANALYZE statement in the SQL standard.
SEE ALSO
VACUUM [vacuum(7)], vacuumdb [vacuumdb(1)], in the documentation, in the documentation
SQL - Language Statements 2010-05-14 ANALYZE(7)
