12.11. Limitations
The current limitations of PostgreSQL 's text search features are:
-
The length of each lexeme must be less than 2 kilobytes
-
No more than 256 positions per lexeme
-
Position values in
tsvectormust be greater than 0 and no more than 16,383 -
The length of a
tsvector's data (lexemes + positions) must be less than 1 megabyte -
The length of a
tsquery's data (lexemes only) must be less than 1 megabyte -
The match distance in a
<(FOLLOWED BY)N>tsqueryoperator cannot be more than 16,384
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.