18th October 2018: PostgreSQL 11 Released!
Supported Versions: Current (11) / 10 / 9.6 / 9.5 / 9.4 / 9.3
Development Versions: devel
Unsupported versions: 9.2 / 9.1 / 9.0 / 8.4 / 8.3

12.11. Limitations

The current limitations of PostgreSQL's text search features are:

  • The length of each lexeme must be less than 2K bytes

  • The length of a tsvector (lexemes + positions) must be less than 1 megabyte

  • The number of lexemes must be less than 264

  • Position values in tsvector must be greater than 0 and no more than 16,383

  • No more than 256 positions per lexeme

  • The number of nodes (lexemes + operators) in a tsquery must be less than 32,768

For comparison, the PostgreSQL 8.1 documentation contained 10,441 unique words, a total of 335,420 words, and the most frequent word "postgresql" was mentioned 6,127 times in 655 documents.

Another example — the PostgreSQL mailing list archives contained 910,989 unique words with 57,491,343 lexemes in 461,020 messages.