max_identifier_length

Definition PG 18 manual

Reports the maximum identifier length. It is determined as one less than the value of NAMEDATALEN when building the server. The default value of NAMEDATALEN is 64; therefore the default max_identifier_length is 63 bytes, which can be less than 63 characters when using multibyte encodings.

How it works

Shows the maximum identifier length. It is read-only and cannot be changed with SET or configuration-file edits.

It exposes NAMEDATALEN minus one; longer unquoted or quoted identifiers are truncated when objects are created.

Interpret it with max_function_args, max_index_keys, block_size. Applications and operations tooling may read max_identifier_length for capability or environment detection, but cannot SET it; cross-cluster comparisons must account for build, initdb, and current-database differences.

Operational considerations

Trying to change read-only max_identifier_length with SET or a configuration file.

Assuming every cluster, database, or vendor build reports the same value.

Ignoring the value in file-format or feature-compatibility checks.

Treating reported metadata as a performance target instead of an environment fact.

Workload guidance

OLAP: Not tunable. Use max_identifier_length to verify format, build, or resource assumptions on analytical nodes and keep every read/write candidate compatible.

OLTP: Not tunable. Record max_identifier_length as a deployment/capability fact; if it is unexpected, fix the binary, initdb, or database-creation process rather than trying SET.

SMALL: Not tunable. Preserve it in inventory and incident reports; do not custom-build or rebuild merely to change it without a demonstrated compatibility need.