Re: Extend GIN

On Sat, Mar 18, 2017 at 11:31 AM, Herman Bergwerf
<hermanbergwerf@gmail.com> wrote:
> Hi! I am building a database with mathematical expressions. For example
> something like '1+x/y'. I want to try to create an index to quickly find
> records that match a pattern like '?a + ?b' ('1+x/y' is an example of this).
> Is this feasible? (the jsquery project is doing something a little like
> this) I do not know much about complicated indexes. I looked at the GIN
> index which is somehow able to index contains and contained by. For example
> in some way 1+x/y contains ?a+?b. I thought about creating a function in Lua
> to check this and create an operator class to make this work with the GIN
> index. Is something like that possible? Could it actually work?

Absolutely.  First place to start is pg_tgrm module.
https://www.postgresql.org/docs/9.6/static/pgtrgm.html

It supports indexing of unanchored LIKE expressions ('%xyz%) and, as
of 9.3, can index certain classes of regular expression.  It got a big
speed boost in 9.6 so go for recent postgres if you can.

merlin