Parameter · Preset Options
max_index_keys
Shows the maximum number of index keys.
- Default:
32 - Type: integer
- Range: 32 … 32
- Applies: Read-only
In plain words
One index can cover at most 32 columns. That includes extra INCLUDE columns of a covering index. It is fixed when PostgreSQL is compiled.
For DBAs and operators
Defined by INDEX_MAX_KEYS (compile time). Error: ERROR: cannot use more than 32 columns in an index. If you are near this limit the index design is usually the problem: B-tree lookups only use leading columns efficiently, and wide indexes are expensive to maintain.
How to change it
Fixed when PostgreSQL was built or the cluster was initialised. You can only read it.