| Function | nl_term_candidates | Returns in an array the candidate search terms from phrase. |
| Function | nl_phrase_search | Return the tsearch2 query that should be used to do a phrase search. |
| Function | _nl_phrase_search | Perform a very simple pruning of the phrase, letting fti do ranking. |
| Function | _slow_nl_phrase_search | Return the tsearch2 query that should be use to do a phrase search. |
| Unknown Field: phrase | a search phrase | |
The precise heuristics applied by this function will vary as we tune the system.
It is the interface by which a user query should be turned into a backend search language query.
Caveats: The model class must define a 'fti' column which is then used used for full text searching.
| Parameters | phrase | A search phrase. |
| table | This should be the SQLBase class representing the base type. | |
| constraints | Additional SQL clause that limits the rows to a subset of the table. | |
| extra_constraints_tables | A list of additional table names that are needed by the constraints clause. | |
| fast_enabled | If true use a fast, but less precise, code path. When feature flags are available this will be converted to a feature flag. | |
| Returns | A tsearch2 query string. | |
This function groups the terms with & clause, and creates an additional & grouping for each subset of terms created by discarding one term.
See nl_phrase_search for the contract of this function.
Return the tsearch2 query that should be use to do a phrase search. This function implement an algorithm similar to the one used by MySQL natural language search (as documented at http://dev.mysql.com/doc/refman/5.0/en/fulltext-search.html). It eliminates stop words from the phrase and normalize each terms according to the full text indexation rules (lowercasing and stemming). Each term that is present in more than 50% of the candidate rows is also eliminated from the query. That term eliminatation is only done when there are 5 candidate rows or more. The remaining terms are then ORed together. One should use the ts_rank() or ts_rank_cd() function to order the results from running that query. This will make rows that use more of the terms and for which the terms are found closer in the text at the top of the list, while still returning rows that use only some of the terms. :terms: Some candidate search terms. :table: This should be the SQLBase class representing the base type. :constraints: Additional SQL clause that limits the rows to a subset of the table. :extra_constraints_tables: A list of additional table names that are needed by the constraints clause. Caveat: The model class must define a 'fti' column which is then used for full text searching.