PostgreSQL partitioning syntax FOR VALUES - postgresql

Question

I'm working on table partitioning in PostgreSQL.
I created a partition for my master table:
CREATE TABLE head_partition_table PARTITION OF master_table
FOR VALUES FROM (DATE_START) TO (DATE_END)
PARTITION BY RANGE (ENTITY_ID, GROUP_NAME);
After that, I want to divide head_partition_table into smaller partitions, so I wrote code:
CREATE TABLE subpartition_table OF head_partititon_table
FOR VALUES FROM ('0', 'A') TO ('0', 'Z');
I can't find how I can specify individual values rather than a range.
Something like
CREATE TABLE subpartition_table OF head_partititon_table
FOR VALUES ('0', 'A');
CREATE TABLE subpartition_table OF head_partititon_table
FOR VALUES ('0', 'Z');
I get a syntax error at or near "(".
Is this possible?
P.S. I tried PARTITION BY LIST, but in that case, I can use just one field.

Answer 1

You could partition these by list like you want by introducing another layer of partitions:
CREATE TABLE head_partition_table PARTITION OF master_table
FOR VALUES FROM ('2019-01-01') TO ('2020-01-01')
PARTITION BY LIST (entity_id);
CREATE TABLE subpartition1 PARTITION OF head_partition_table
FOR VALUES IN ('0')
PARTITION BY LIST (group_name);
CREATE TABLE subsubpartition1 PARTITION OF subpartition1
FOR VALUES IN ('A');
But this is more an academic exercise than something useful.
Anything exceeding a at most few hundred partitions will not perform well at all.