Wiki / Configuration Parameters

The planner will rewrite explicit JOIN constructs (except FULL JOINs) into lists of FROM items whenever a list of no more than this many items would result. Smaller values reduce planning time but might yield inferior query plans. By default, this variable is set the same as from_collapse_limit, which is appropriate for most uses. Setting it to 1 prevents any reordering of explicit JOINs. Thus, the explicit join order specified in the query will be the actual order in which the relations are joined. Because the query planner does not always choose the optimal join order, advanced users can elect to temporarily set this variable to 1, and then specify the join order they desire explicitly. For more information see Section 14.3. Setting this value to geqo_threshold or more may trigger use of the GEQO planner, resulting in non-optimal plans. See Section 19.7.3.

English manual coverage begins with PostgreSQL 7.4. Source history and runtime observations have their own recorded version boundaries.

boot val

8

category

Query Tuning / Other Planner Options

context

user

documented

true

enumvals

Unknown

extra desc

The planner will flatten explicit JOIN constructs into lists of FROM items whenever a list of no more than this many items would result.

lang

en

max val

2147483647

metadata version

18

min val

1

name

join_collapse_limit

short desc

Sets the FROM-list size beyond which JOIN constructs are not flattened.

source

pg-settings-source-snapshot

unit

Unknown

vartype

integer