| Postgres-XC 1.2devel Documentation | ||||
|---|---|---|---|---|
| Prev | Fast Backward | Chapter 12. Full Text Search | Fast Forward | Next |
Note: The following description applies both to Postgres-XC and PostgreSQL if not described explicitly. You can read PostgreSQL as Postgres-XC except for version number, which is specific to each product.
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.