PAX: support varchar min/max operator

The operator of varchar does not exist in pg_operator.dat, but it have same oper with text.
This is because the type which can be cast picked in the oper() function.

Current change support the varchar min/max operator in PAX.

Author: jiaqizho

contrib/pax_storage/expected/statistics.out

@@ -3,7 +3,7 @@ set default_table_access_method = pax;
 -- Test with small group
 -- 
 set pax_max_tuples_per_group = 10;
--- overview
+-- test min/max type support
 create table t1(v1 int, v2 text, v3 float8, v4 bool) with (minmax_columns='v1,v2,v3,v4');
 NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'v1' as the Cloudberry Database data distribution key for this table.
 HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
@@ -17,6 +17,19 @@ select * from get_pax_aux_table('t1');
 (3 rows)
 
 drop table t1;
+create table t2(v1 bpchar, v2 bpchar(20), v3 varchar(20), v4 varchar(20)) with (minmax_columns='v1,v2,v3,v4');
+NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'v1' as the Cloudberry Database data distribution key for this table.
+HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
+insert into t2 select i::bpchar,i::bpchar,i::varchar, i::varchar from generate_series(1, 1000)i;
+select * from get_pax_aux_table('t2');
+ ptblockname | pttupcount |                                                                                       ptstatistics                                                                                       | ptexistvisimap | ptexistexttoast | ptisclustered 
+-------------+------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------+-----------------+---------------
+ 0           |        322 | [(false,false),(322),(1,998),None],[(false,false),(322),(1                   ,998                 ),None],[(false,false),(322),(1,998),None],[(false,false),(322),(1,998),None]          | f              | f               | f
+ 0           |        340 | [(false,false),(340),(1000,999),None],[(false,false),(340),(1000                ,999                 ),None],[(false,false),(340),(1000,999),None],[(false,false),(340),(1000,999),None] | f              | f               | f
+ 0           |        338 | [(false,false),(338),(101,997),None],[(false,false),(338),(101                 ,997                 ),None],[(false,false),(338),(101,997),None],[(false,false),(338),(101,997),None]    | f              | f               | f
+(3 rows)
+
+drop table t2;
 -- test `hasnull/allnull`/`count`, not need setting the minmax_columns
 create table t1(v1 int, v2 float8);
 NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'v1' as the Cloudberry Database data distribution key for this table.

contrib/pax_storage/sql/statistics.sql

@@ -6,12 +6,17 @@ set default_table_access_method = pax;
 -- 
 set pax_max_tuples_per_group = 10;
 
--- overview
+-- test min/max type support
 create table t1(v1 int, v2 text, v3 float8, v4 bool) with (minmax_columns='v1,v2,v3,v4');
 insert into t1 select i,i::text,i::float8, i % 2 > 0 from generate_series(1, 1000)i;
 select * from get_pax_aux_table('t1');
 drop table t1;
 
+create table t2(v1 bpchar, v2 bpchar(20), v3 varchar(20), v4 varchar(20)) with (minmax_columns='v1,v2,v3,v4');
+insert into t2 select i::bpchar,i::bpchar,i::varchar, i::varchar from generate_series(1, 1000)i;
+select * from get_pax_aux_table('t2');
+drop table t2;
+
 -- test `hasnull/allnull`/`count`, not need setting the minmax_columns
 create table t1(v1 int, v2 float8);
 

contrib/pax_storage/src/cpp/storage/oper/pax_oper.cc

@@ -814,6 +814,18 @@ std::map<OperMinMaxKey, OperMinMaxFunc> min_max_opers = {
     INIT_MIN_MAX_OPER(BPCHAROID, BPCHAROID, BTGreaterStrategyNumber,
                       textop::BpCharGT),
 
+    // oper(varchar, varchar)
+    INIT_MIN_MAX_OPER(VARCHAROID, VARCHAROID, BTLessStrategyNumber,
+                      textop::TextLT),
+    INIT_MIN_MAX_OPER(VARCHAROID, VARCHAROID, BTLessEqualStrategyNumber,
+                      textop::TextLE),
+    INIT_MIN_MAX_OPER(VARCHAROID, VARCHAROID, BTEqualStrategyNumber,
+                      textop::TextEQ),
+    INIT_MIN_MAX_OPER(VARCHAROID, VARCHAROID, BTGreaterEqualStrategyNumber,
+                      textop::TextGE),
+    INIT_MIN_MAX_OPER(VARCHAROID, VARCHAROID, BTGreaterStrategyNumber,
+                      textop::TextGT),
+
     // oper(numeric, numeric)
     INIT_MIN_MAX_OPER(NUMERICOID, NUMERICOID, BTLessStrategyNumber,
                       numericop::NumericLT),
@@ -827,8 +839,6 @@ std::map<OperMinMaxKey, OperMinMaxFunc> min_max_opers = {
                       numericop::NumericGT),
 
     // FIXME(jiaqizho): support below oper in the feature
-    // BPCHAROID
-    // VARCHAROID
     // TIMESTAMPTZOID
     // TIMEOID
     // TIMESTAMPOID