Check statistics targets in PostgreSQL

Question

I have searched but been unable to find any simple, straight forward answer to this. How do I check the current statistics targets used by ANALYZE?

Answer 1

The setting for the statistics target is stored per column in the catalog table pg_attribute. You can set it like this:

ALTER TABLE myschama.mytable ALTER mycolumn SET STATISTICS 127;

And check it like this:

SELECT attstattarget
FROM   pg_attribute
WHERE  attrelid = 'myschama.mytable'::regclass
AND    attname = 'mycolumn';

Or you just look at the creation script in the object browser of pgAdmin, where it is appended if the value is distinct from the default in default_statistics_target.

I quote the manual on attstattarget:

attstattarget controls the level of detail of statistics accumulated for this column by ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of "most common values" to collect, and the target number of histogram bins to create.

Bold emphasis mine.

Answer 2

This provides a cleaner view of current statistics being collected

SELECT attrelid::regclass, attname, attstattarget FROM pg_attribute WHERE attstattarget >= 0 order by attstattarget desc;