Fix compressed sort pushdown to respect collation (#10182)

Fixes #9998

Author: natalya-aksman

.unreleased/pr_10182

@@ -0,0 +1 @@
+Fixes: #10182 Fix columnstore sort pushdown to check for different query sortkey collation

tsl/src/nodes/columnar_scan/columnar_scan.c

@@ -2921,6 +2921,12 @@ match_pathkeys_to_compression_orderby(List *pathkeys, List *chunk_em_exprs,
 		{
 			return false;
 		}
+		/* Pathkey collation different from underlying column collation may lead to different sort
+		 * order */
+		if (var->varcollid != pk->pk_eclass->ec_collation)
+		{
+			return false;
+		}
 
 		char *column_name = get_attname(compression_info->chunk_rte->relid, var->varattno, false);
 		int orderby_index = ts_array_position(compression_info->settings->fd.orderby, column_name);

tsl/test/expected/compressed_collation.out

@@ -119,3 +119,33 @@ select min(name), max(name) from collation_agg_c;
 
 reset enable_sort;
 reset timescaledb.debug_require_vector_agg;
+-- Test #9998: should not match query sort key with a different collation to compressed index sort key
+create table t9998 (
+    ts   timestamptz not null,
+    name text collate :"COLLATION"
+);
+select table_name from create_hypertable('t9998', 'ts');
+ table_name 
+------------
+ t9998
+
+insert into t9998 values
+    ('2024-01-01', 'B'),
+    ('2024-01-01', 'a');
+alter table t9998 set (
+    timescaledb.compress,
+    timescaledb.compress_orderby = 'name'
+);
+select count(compress_chunk(ch)) from show_chunks('t9998') ch;
+ count 
+-------
+     1
+
+-- C collation sorts capital before lowercase: expected order is 'B', 'a'.
+select name from t9998 order by name collate "C";
+ name 
+------
+ B
+ a
+
+drop table t9998 cascade;

tsl/test/sql/compressed_collation.sql

@@ -102,3 +102,23 @@ select min(name), max(name) from collation_agg_c;
 
 reset enable_sort;
 reset timescaledb.debug_require_vector_agg;
+
+-- Test #9998: should not match query sort key with a different collation to compressed index sort key
+create table t9998 (
+    ts   timestamptz not null,
+    name text collate :"COLLATION"
+);
+select table_name from create_hypertable('t9998', 'ts');
+insert into t9998 values
+    ('2024-01-01', 'B'),
+    ('2024-01-01', 'a');
+alter table t9998 set (
+    timescaledb.compress,
+    timescaledb.compress_orderby = 'name'
+);
+select count(compress_chunk(ch)) from show_chunks('t9998') ch;
+
+-- C collation sorts capital before lowercase: expected order is 'B', 'a'.
+select name from t9998 order by name collate "C";
+
+drop table t9998 cascade;