ANALYZE(7)

✨ ANALYZE(7) ✨

Hey bestie, welcome to the ANALYZE(7) page from the PostgreSQL 13.23 docs! This is literally the glow-up your database stats have been waiting for. 💅

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🌸 NAME 🌸

ANALYZE — collect statistics about a database. It's giving data-gathering queen 👑

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✨ SYNOPSIS ✨

ANALYZE [ ( option [, ...] ) ] [ table_and_columns [, ...] ]
ANALYZE [ VERBOSE ] [ table_and_columns [, ...] ]

where option can be one of:

VERBOSE [ boolean ]
SKIP_LOCKED [ boolean ]

and table_and_columns is:

table_name [ ( column_name [, ...] ) ]

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💖 DESCRIPTION 💖

OK so picture this: ANALYZE collects statistics about what's inside the tables in your database, and stashes all those results in the pg_statistic system catalog. Then the query planner is like "omg thank you bestie" and uses those stats to figure out the most efficient execution plans for your queries. Literally main character energy for the planner. 🌟

If you don't give it a table_and_columns list, ANALYZE processes every table and materialized view in the current database that you (the current user) have permission to analyze. Iconic, generous, covers everything. But if you do give it a list, it processes only those table(s). And get this — you can also give a list of column names for a table, in which case only the statistics for those columns get collected. So specific, so curated. 🎯

When the option list is wrapped in parentheses, the options can be written in any order. The parenthesized syntax was added in PostgreSQL 11, and the unparenthesized syntax is deprecated. So like, use the parentheses, bestie. It's the moment. ⚠️

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🦋 PARAMETERS 🦋

• VERBOSE — Turns on progress messages so you can see what's happening. She's chatty and we love that. 💬
• SKIP_LOCKED — Says that ANALYZE should NOT wait for any conflicting locks to be released when it starts working on a relation: if a relation can't be locked immediately without waiting, the relation just gets skipped. No waiting around, no drama. ⏭️ Note though — even with this option, ANALYZE may still block when opening the relation's indexes or when acquiring sample rows from partitions, table inheritance children, and some types of foreign tables. Also, while ANALYZE ordinarily processes all partitions of specified partitioned tables, this option will cause ANALYZE to skip all partitions if there's a conflicting lock on the partitioned table. So it's giving "skip everything" energy in that case. 💀
• boolean — Specifies whether the selected option should be turned on or off. You can write TRUE, ON, or 1 to enable the option, and FALSE, OFF, or 0 to disable it. The boolean value can also be omitted, in which case TRUE is assumed. Default behavior stays winning. ✨
• table_name — The name (possibly schema-qualified) of a specific table to analyze. If omitted, all regular tables, partitioned tables, and materialized views in the current database are analyzed (but not foreign tables — they don't get the invite by default 🙈). If the specified table is a partitioned table, both the inheritance statistics of the partitioned table as a whole AND the statistics of the individual partitions are updated. It's a full family update. 👑
• column_name — The name of a specific column to analyze. Defaults to all columns. Because sometimes you just want to focus on the one column that's been acting up. 🎀

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🌈 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. It's literally narrating its own journey and honestly? We stan a transparent icon. 📢

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💜 NOTES 💜

Okay so here's the tea on permissions: to analyze a table, one must ordinarily be the table's owner or a superuser. BUT — database owners are allowed to analyze all tables in their databases, except shared catalogs. (The restriction for shared catalogs means that a true database-wide ANALYZE can only be performed by a superuser.) So like, there's levels to this. 👑 ANALYZE will skip over any tables that the calling user does not have permission to analyze. No forcing it, no sneaking in. 🚫

Foreign tables are analyzed only when explicitly selected. Not all foreign data wrappers support ANALYZE. If the table's wrapper does not support ANALYZE, the command prints a warning and does nothing. It's giving "we tried, we warned, we moved on." 😭

In the default PostgreSQL configuration, the autovacuum daemon (see Section 24.1.6) takes care of automatic analyzing of tables when they're first loaded with data, and as they change throughout regular operation. So it's lowkey doing the work for you. But when autovacuum is disabled, it's 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 choose the most appropriate query plan, and thereby improve the speed of query processing. A common strategy for read-mostly databases is to run VACUUM(7) and ANALYZE once a day during a low-usage time of day. (This will not be sufficient if there's heavy update activity.) So like, if your database is busy, do more. Fr fr. 📅

ANALYZE requires only a read lock on the target table, so it can run in parallel with other activity on the table. It's considerate like that. 🫶

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's more information about the statistics in Chapter 24. It's giving "I'll include what matters and leave the rest." 🎯

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. So efficient! But note — the statistics are only approximate, and will change slightly each time ANALYZE 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(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. Zero effort for zero-use columns, honestly valid. 🍓

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. So like, more accuracy = more work. Balance, bestie. ⚖️

One of the values estimated by ANALYZE is the number of distinct values that appear in each column. Because only a subset of the rows are examined, this estimate can sometimes be quite inaccurate, even with the largest possible statistics target. If this inaccuracy leads to bad query plans, a more accurate value can be determined manually and then installed with ALTER TABLE ... ALTER COLUMN ... SET (n_distinct = ...) (see ALTER TABLE (ALTER_TABLE(7))). So you can literally override it if you know better. Manual mode activated. 💪

If the table being analyzed has inheritance children, ANALYZE gathers two sets of statistics: one on the rows of the parent table only, and a second including rows of both the parent table and all of its children. This second set of statistics is needed when planning queries that process the inheritance tree as a whole. The child tables themselves are not individually analyzed in this case. The autovacuum daemon, however, will only consider inserts or updates on the parent table itself when deciding whether to trigger an automatic analyze for that table. If that table is rarely inserted into or updated, the inheritance statistics will not be up to date unless you run ANALYZE manually. So like, sometimes you gotta do it yourself. 🙋‍♀️

For partitioned tables, ANALYZE gathers statistics by sampling rows from all partitions; in addition, it will recurse into each partition and update its statistics. Each leaf partition is analyzed only once, even with multi-level partitioning. No statistics are collected for only the parent table (without data from its partitions), because with partitioning it's guaranteed to be empty. Periodt. 💅

The autovacuum daemon does not process partitioned tables, nor does it process inheritance parents if only the children are ever modified. It is usually necessary to periodically run a manual ANALYZE to keep the statistics of the table hierarchy up to date. So like, set a reminder bestie. ⏰

If any child tables or partitions are foreign tables whose foreign data wrappers do not support ANALYZE, those tables are ignored while gathering inheritance statistics. They just don't participate, and that's fine. 🙈

If the table being analyzed is completely empty, ANALYZE will not record new statistics for that table. Any existing statistics will be retained. Empty table? Old stats stay. She doesn't overwrite with nothing. 💀

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🌟 COMPATIBILITY 🌟

There is no ANALYZE statement in the SQL standard. We're built different. 💅

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🎀 SEE ALSO 🎀

VACUUM(7), vacuumdb(1), Section 19.4.4, Section 24.1.6

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Okay bestie, that's the whole page! This was ANALYZE(7) from PostgreSQL 13.23, brought to you with love and stats, dated 2025. Go forth and collect those statistics like the icon you are. 🦋✨👑