Rework code to determine partition pruning procedure

Amit Langote reported that partition prune was unable to work with
arrays, enums, etc, which led him to research the appropriate way to
match query clauses to partition keys: instead of searching for an exact
match of the expression's type, it is better to rely on the fact that
the expression qual has already been resolved to a specific operator,
and that the partition key is linked to a specific operator family.
With that info, it's possible to figure out the strategy and comparison
function to use for the pruning clause in a manner that works reliably
for pseudo-types also.

Include new test cases that demonstrate pruning where pseudotypes are
involved.

Author: Amit Langote, Álvaro Herrera
Discussion: https://postgr.es/m/2b02f1e9-9812-9c41-972d-517bdc0f815d@lab.ntt.co.jp

src/test/regress/expected/partition_prune.out

@@ -2599,3 +2599,141 @@ select * from boolp where a = (select value from boolvalues where not value);
 
 drop table boolp;
 reset enable_indexonlyscan;
+--
+-- check that pruning works properly when the partition key is of a
+-- pseudotype
+--
+-- array type list partition key
+create table pp_arrpart (a int[]) partition by list (a);
+create table pp_arrpart1 partition of pp_arrpart for values in ('{1}');
+create table pp_arrpart2 partition of pp_arrpart for values in ('{2, 3}', '{4, 5}');
+explain (costs off) select * from pp_arrpart where a = '{1}';
+               QUERY PLAN               
+----------------------------------------
+ Append
+   ->  Seq Scan on pp_arrpart1
+         Filter: (a = '{1}'::integer[])
+(3 rows)
+
+explain (costs off) select * from pp_arrpart where a = '{1, 2}';
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+explain (costs off) select * from pp_arrpart where a in ('{4, 5}', '{1}');
+                              QUERY PLAN                              
+----------------------------------------------------------------------
+ Append
+   ->  Seq Scan on pp_arrpart1
+         Filter: ((a = '{4,5}'::integer[]) OR (a = '{1}'::integer[]))
+   ->  Seq Scan on pp_arrpart2
+         Filter: ((a = '{4,5}'::integer[]) OR (a = '{1}'::integer[]))
+(5 rows)
+
+drop table pp_arrpart;
+-- array type hash partition key
+create table pph_arrpart (a int[]) partition by hash (a);
+create table pph_arrpart1 partition of pph_arrpart for values with (modulus 2, remainder 0);
+create table pph_arrpart2 partition of pph_arrpart for values with (modulus 2, remainder 1);
+insert into pph_arrpart values ('{1}'), ('{1, 2}'), ('{4, 5}');
+select tableoid::regclass, * from pph_arrpart order by 1;
+   tableoid   |   a   
+--------------+-------
+ pph_arrpart1 | {1,2}
+ pph_arrpart1 | {4,5}
+ pph_arrpart2 | {1}
+(3 rows)
+
+explain (costs off) select * from pph_arrpart where a = '{1}';
+               QUERY PLAN               
+----------------------------------------
+ Append
+   ->  Seq Scan on pph_arrpart2
+         Filter: (a = '{1}'::integer[])
+(3 rows)
+
+explain (costs off) select * from pph_arrpart where a = '{1, 2}';
+                QUERY PLAN                
+------------------------------------------
+ Append
+   ->  Seq Scan on pph_arrpart1
+         Filter: (a = '{1,2}'::integer[])
+(3 rows)
+
+explain (costs off) select * from pph_arrpart where a in ('{4, 5}', '{1}');
+                              QUERY PLAN                              
+----------------------------------------------------------------------
+ Append
+   ->  Seq Scan on pph_arrpart1
+         Filter: ((a = '{4,5}'::integer[]) OR (a = '{1}'::integer[]))
+   ->  Seq Scan on pph_arrpart2
+         Filter: ((a = '{4,5}'::integer[]) OR (a = '{1}'::integer[]))
+(5 rows)
+
+drop table pph_arrpart;
+-- enum type list partition key
+create type pp_colors as enum ('green', 'blue', 'black');
+create table pp_enumpart (a pp_colors) partition by list (a);
+create table pp_enumpart_green partition of pp_enumpart for values in ('green');
+create table pp_enumpart_blue partition of pp_enumpart for values in ('blue');
+explain (costs off) select * from pp_enumpart where a = 'blue';
+               QUERY PLAN                
+-----------------------------------------
+ Append
+   ->  Seq Scan on pp_enumpart_blue
+         Filter: (a = 'blue'::pp_colors)
+(3 rows)
+
+explain (costs off) select * from pp_enumpart where a = 'black';
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+drop table pp_enumpart;
+drop type pp_colors;
+-- record type as partition key
+create type pp_rectype as (a int, b int);
+create table pp_recpart (a pp_rectype) partition by list (a);
+create table pp_recpart_11 partition of pp_recpart for values in ('(1,1)');
+create table pp_recpart_23 partition of pp_recpart for values in ('(2,3)');
+explain (costs off) select * from pp_recpart where a = '(1,1)'::pp_rectype;
+                QUERY PLAN                 
+-------------------------------------------
+ Append
+   ->  Seq Scan on pp_recpart_11
+         Filter: (a = '(1,1)'::pp_rectype)
+(3 rows)
+
+explain (costs off) select * from pp_recpart where a = '(1,2)'::pp_rectype;
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+drop table pp_recpart;
+drop type pp_rectype;
+-- range type partition key
+create table pp_intrangepart (a int4range) partition by list (a);
+create table pp_intrangepart12 partition of pp_intrangepart for values in ('[1,2]');
+create table pp_intrangepart2inf partition of pp_intrangepart for values in ('[2,)');
+explain (costs off) select * from pp_intrangepart where a = '[1,2]'::int4range;
+                QUERY PLAN                
+------------------------------------------
+ Append
+   ->  Seq Scan on pp_intrangepart12
+         Filter: (a = '[1,3)'::int4range)
+(3 rows)
+
+explain (costs off) select * from pp_intrangepart where a = '(1,2)'::int4range;
+        QUERY PLAN        
+--------------------------
+ Result
+   One-Time Filter: false
+(2 rows)
+
+drop table pp_intrangepart;

src/test/regress/sql/partition_prune.sql

@@ -645,3 +645,56 @@ select * from boolp where a = (select value from boolvalues where not value);
 drop table boolp;
 
 reset enable_indexonlyscan;
+
+--
+-- check that pruning works properly when the partition key is of a
+-- pseudotype
+--
+
+-- array type list partition key
+create table pp_arrpart (a int[]) partition by list (a);
+create table pp_arrpart1 partition of pp_arrpart for values in ('{1}');
+create table pp_arrpart2 partition of pp_arrpart for values in ('{2, 3}', '{4, 5}');
+explain (costs off) select * from pp_arrpart where a = '{1}';
+explain (costs off) select * from pp_arrpart where a = '{1, 2}';
+explain (costs off) select * from pp_arrpart where a in ('{4, 5}', '{1}');
+drop table pp_arrpart;
+
+-- array type hash partition key
+create table pph_arrpart (a int[]) partition by hash (a);
+create table pph_arrpart1 partition of pph_arrpart for values with (modulus 2, remainder 0);
+create table pph_arrpart2 partition of pph_arrpart for values with (modulus 2, remainder 1);
+insert into pph_arrpart values ('{1}'), ('{1, 2}'), ('{4, 5}');
+select tableoid::regclass, * from pph_arrpart order by 1;
+explain (costs off) select * from pph_arrpart where a = '{1}';
+explain (costs off) select * from pph_arrpart where a = '{1, 2}';
+explain (costs off) select * from pph_arrpart where a in ('{4, 5}', '{1}');
+drop table pph_arrpart;
+
+-- enum type list partition key
+create type pp_colors as enum ('green', 'blue', 'black');
+create table pp_enumpart (a pp_colors) partition by list (a);
+create table pp_enumpart_green partition of pp_enumpart for values in ('green');
+create table pp_enumpart_blue partition of pp_enumpart for values in ('blue');
+explain (costs off) select * from pp_enumpart where a = 'blue';
+explain (costs off) select * from pp_enumpart where a = 'black';
+drop table pp_enumpart;
+drop type pp_colors;
+
+-- record type as partition key
+create type pp_rectype as (a int, b int);
+create table pp_recpart (a pp_rectype) partition by list (a);
+create table pp_recpart_11 partition of pp_recpart for values in ('(1,1)');
+create table pp_recpart_23 partition of pp_recpart for values in ('(2,3)');
+explain (costs off) select * from pp_recpart where a = '(1,1)'::pp_rectype;
+explain (costs off) select * from pp_recpart where a = '(1,2)'::pp_rectype;
+drop table pp_recpart;
+drop type pp_rectype;
+
+-- range type partition key
+create table pp_intrangepart (a int4range) partition by list (a);
+create table pp_intrangepart12 partition of pp_intrangepart for values in ('[1,2]');
+create table pp_intrangepart2inf partition of pp_intrangepart for values in ('[2,)');
+explain (costs off) select * from pp_intrangepart where a = '[1,2]'::int4range;
+explain (costs off) select * from pp_intrangepart where a = '(1,2)'::int4range;
+drop table pp_intrangepart;