PostgreSQL full text search and 'unaccented'

[hans@dykema.nl]

When enabling full text search, it could be convenient to let PostgreSQL search without accents.
This can be enabled using the right text search engines.
Here's some instruction:

When one gets this:

crm_divertimento=# create extension unaccent;
ERROR: extension "unaccent" is not available

One needs to install the progresql contrib package or build postgresql with 'make world'.

Now, to enable full text search without accents, the following can be done:

crm_divertimento=# create extension unaccent;
CREATE EXTENSION
​
crm_divertimento=# show default_text_search_config;
default_text_search_config
----------------------------
pg_catalog.dutch
(1 row)
​
crm_divertimento=# create text search configuration dutch_unaccented(COPY = dutch);
CREATE TEXT SEARCH CONFIGURATION
crm_divertimento=# alter text search configuration dutch_unaccented alter mapping for hword, hword_part, word with unaccent, dutch_stem;
ALTER TEXT SEARCH CONFIGURATION
​

Next in postgresql.conf enable the new text search configuration:

(...)
# default configuration for text search
default_text_search_config = 'pg_catalog.dutch_unaccented'
(...)

And restart the postgresql service.

Now

 to_tsvector('dutch_unaccented', 'Dvořák, Antonín - Carnival Overture, op.92, B.169 (Karneval)')

will result in

'antonin':2 'b.169':6 'carnival':3 'dvorak':1 'karneval':7 'op.92':5 'overtur':4

instead of

'antonin':2 'b.169':6 'carnival':3 'dvořak':1 'karneval':7 'op.92':5 'overtur':4

See the accent on the 'r'.