Hi hackers.
I tried to create LSM AM which can be used instead of nbtree.
I looked at contrib/btree/gin, contrib/isn and try to do the following:
CREATE OPERATOR FAMILY lsm3_float_ops USING lsm3;
CREATE OPERATOR CLASS float4_ops DEFAULT
FOR TYPE float4 USING lsm3 FAMILY lsm3_float_ops AS
OPERATOR 1 <,
OPERATOR 2 <=,
OPERATOR 3 =,
OPERATOR 4 >=,
OPERATOR 5 >,
FUNCTION 1 btfloat4cmp(float4,float4);
CREATE OPERATOR CLASS float8_ops DEFAULT
FOR TYPE float8 USING lsm3 FAMILY lsm3_float_ops AS
OPERATOR 1 <,
OPERATOR 2 <=,
OPERATOR 3 =,
OPERATOR 4 >=,
OPERATOR 5 >,
FUNCTION 1 btfloat8cmp(float8,float8);
ALTER OPERATOR FAMILY lsm3_float_ops USING lsm3 ADD
OPERATOR 1 < (float4,float8),
OPERATOR 1 < (float8,float4),
OPERATOR 2 <= (float4,float8),
OPERATOR 2 <= (float8,float4),
OPERATOR 3 = (float4,float8),
OPERATOR 3 = (float8,float4),
OPERATOR 4 >= (float4,float8),
OPERATOR 4 >= (float8,float4),
OPERATOR 5 > (float4,float8),
OPERATOR 5 > (float8,float4),
FUNCTION 1 btfloat48cmp(float4,float8),
FUNCTION 1 btfloat84cmp(float8,float4);
But then I get error for btfloat48cmp and btfloat84cmp functions:
ERROR: associated data types must be specified for index support function
If I replace lsm3 with btree in ALTER FAMILY, then there is no error.
I wonder if it is possible in Postgres to define custom index, which can
handle comparison of different types, i.e.
create table t(pk bigint);
create index on t using lsm3(pk);
select * from t where pk=1;
I failed to make Postgres use index in this case. Index is used only if
I rewrite this query in this way:
select * from t where pk=1::bigint;
Thanks in advance,
Konstantin
