PostgreSQL index array of int4range using GIN - custom operator class - postgresql

Question

Here is my table:
CREATE TABLE
mytable
(
id INT NOT NULL PRIMARY KEY,
val int4range[]
);
I want to index the val column:
CREATE INDEX
ix_mytable_val
ON mytable
USING GIN (INT4RANGE(val, '[]')); // error, as is GIN(val)
I came up with the following:
CREATE OPERATOR CLASS gin_int4range_ops
DEFAULT FOR TYPE int4range[] USING gin AS
OPERATOR 1 <(anyrange,anyrange),
OPERATOR 2 <=(anyrange,anyrange),
OPERATOR 3 =(anyrange,anyrange),
OPERATOR 4 >=(anyrange,anyrange),
OPERATOR 5 >(anyrange,anyrange),
FUNCTION 1 lower(anyrange),
FUNCTION 2 upper(anyrange),
FUNCTION 3 isempty(anyrange),
FUNCTION 4 lower_inc(anyrange),
FUNCTION 5 upper_inc(anyrange);
But when I try to create the index, it fails (error below). However, if I call the create from within a DO $$ block, it executes.
If the create index executed, I get the error on INSERT INTO instead.
"ERROR: cache lookup failed for type 1"
I also tried this:
OPERATOR 1 &&(anyrange,anyrange),
OPERATOR 2 <#(anyrange,anyrange),
OPERATOR 3 #>(anyrange,anyrange),
OPERATOR 4 =(anyrange,anyrange),
In order to try and solve this, I have rebooted PG, the machine, and vacuumed the DB. I believe there is an error in the CREATE OPERATOR code.
If I can index an array of custom type of (int, int4range), that would be even better.
I've spent quite some time (a full day) wading through documentation, forums, etc., but can find nothing that really helps me to understand how to solve this (i.e. create a working custom operator class).

Answer 1

You need to CREATE OPERATOR CLASS based on Range Functions and Operators, for example:
CREATE OPERATOR CLASS gin_int4range_ops
DEFAULT FOR TYPE int4range[] USING gin AS
OPERATOR 1 =(anyrange,anyrange),
FUNCTION 1 lower(anyrange),
FUNCTION 2 upper(anyrange),
FUNCTION 3 isempty(anyrange),
FUNCTION 4 lower_inc(anyrange),
FUNCTION 5 upper_inc(anyrange);
Now you can CREATE INDEX:
CREATE INDEX ix_mytable4_vhstore_low
ON mytable USING gin (val gin_int4range_ops);
Check also:
Operator Classes and Operator Families
CREATE OPERATOR CLASS
The following query shows all defined operator classes:
SELECT am.amname AS index_method,
opc.opcname AS opclass_name
FROM pg_am am, pg_opclass opc
WHERE opc.opcmethod = am.oid
ORDER BY index_method, opclass_name;
This query shows all defined operator families and all the operators included in each family:
SELECT am.amname AS index_method,
opf.opfname AS opfamily_name,
amop.amopopr::regoperator AS opfamily_operator
FROM pg_am am, pg_opfamily opf, pg_amop amop
WHERE opf.opfmethod = am.oid AND
amop.amopfamily = opf.oid
ORDER BY index_method, opfamily_name, opfamily_operator;