On Mon, May 2, 2016 at 8:16 AM, David G. Johnston < david.g.johns...@gmail.com> wrote:
> On Sun, May 1, 2016 at 7:27 PM, drum.lu...@gmail.com <drum.lu...@gmail.com > > wrote: > > Repeating the query to improve the self-containment aspect of the email > would have been appreciated. > > >> >> if possible please have a look on the explain analyze results: >> >> http://explain.depesz.com/s/rHOU >> >> What else can I do? >> >> *The indexes I created is:* >> - CREATE INDEX CONCURRENTLY ix_inode_segments_notes_clientids2 ON >> gorfs.inode_segments USING btree ("full_path"); >> >> > the only condition that could even potentially use this index is: > > s.full_path ~ '/userfiles/account/[0-9]+/[a-z]+/[0-9]+' > > My knowledge is limited in this area, and the documentation covers this > specific dynamic only minimally, but for certain attempting to perform an > un-anchored regexp match using a btree index is impossible. > > These leaves to avenues to explore. > > 1) See if a start-of-string anchor will make the btree index usable > 2) Use the pg_trgm contrib module > > http://www.postgresql.org/docs/current/static/pgtrgm.html > > - CREATE INDEX CONCURRENTLY ix_inodes_checksum_st_size ON gorfs.inodes >> USING btree ("checksum_md5","st_size"); >> > > This one was used. > > IMO you are leaving too much infomation encoded in the full_path. I'd > personally setup triggers to parse out the components on insert/update into > fields and then index those fields. In fact I'd probably use some form of > inheritance or other one-to-one relationship here. > > I guess it is documented, I just needed to look a bit more. """ The optimizer can also use a B-tree index for queries involving the pattern matching operators LIKE and ~ if the pattern is a constant and is anchored to the beginning of the string — for example, col LIKE 'foo%' or col ~ '^foo', but not col LIKE '%bar'. However, if your database does not use the C locale you will need to create the index with a special operator class to support indexing of pattern-matching queries; see Section 11.9 below. It is also possible to use B-tree indexes for ILIKE and ~*, but only if the pattern starts with non-alphabetic characters, i.e., characters that are not affected by upper/lower case conversion. """ http://www.postgresql.org/docs/current/static/indexes-types.html David J.
