On Wed, Mar 16, 2011 at 12:15 PM, Travis Orr <t...@ivl.com> wrote: > Can someone enlighten me about this. To me a lot of the details appear > to be hidden since my main SongTable is a FTS3 virtual table.
You don't provide your schema, but based on your queries, I'll make unwarranted assumptions :-). In fts3, there is a rowid column (standard SQLite meaning), a docid column which is an alias of rowid, and all the columns you define are TEXT columns. If you say: CREATE VIRTUAL TABLE MyTable USING FTS3( songid INTEGER PRIMARY KEY AUTO_INCREMENT MAGIC KEYWORDS, title VARCHAR(23), recorded DATETIME ); All three of those columns are TEXT.. Based on your queries, I'm betting that you're assuming that the various typing keywords for a CREATE TABLE statement apply, but they don't. If you want to know why, you can scan the archives or read the source code, but suffice to say that this is the truth at this time. Anyhow, the gist of it is that the FTS3 table has a full-text index on the TEXT of the columns, and that any other queries will be full table scans, as if there were no optimizations at all. So complicated queries with ORDER BY, LIMIT, and OFFSET can absolutely destroy performance if your result sets are all all big (or can be big, watch for the query of death!). If you will not be using MATCH, then there is no gain at all from FTS3, and you should consider just using a regular table. As I understand your problem, the solution I'd probably use would be to create a new temporary table to hold the data while scanning it. So something like: CREATE TEMPORARY TABLE MyResults AS SELECT docid, title, artist FROM songtable WHERE ... ORDER BY ...; I _think_ the resulting table will effectively capture the ORDER BY results, so you can then scan it using OFFSET and LIMIT (or rowid) efficiently. If this is too big, you could experiment with capturing only the docid values in order, and then joining MyResults back against songtable to get the original values. That won't be particularly efficient with OFFSET and LIMIT, but it should be able to join directly with songtable.docid, so it shouldn't be particularly inefficient, either. Of course, you could also just read the entire docid set into memory and manage it that way. It's a little cumbersome because then you have to keep re-binding the query to walk through things, but it probably won't perform any worse. -scott _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
