12.11. Limitations #

   The current limitations of PostgreSQL's text search features are:
     * The length of each lexeme must be less than 2 kilobytes
     * The length of a tsvector (lexemes + positions) must be less than 1
       megabyte
     * The number of lexemes must be less than 2^64
     * Position values in tsvector must be greater than 0 and no more than
       16,383
     * The match distance in a <N> (FOLLOWED BY) tsquery operator cannot
       be more than 16,384
     * 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.