From 56b14592419ea73dc81fcb94b96df9d4ae9d2aac Mon Sep 17 00:00:00 2001
From: Piotr Findeisen <piotr.findeisen@gmail.com>
Date: Tue, 3 Oct 2023 16:11:52 +0200
Subject: [PATCH] Query table_comments without unrolling with UNION ALL

`table_comments` is equally "hard" for the engine as
`information_schema.columns`. Avoid optimizing the query on the `dbt`
side by sending `UNION ALL` with individual schemas. Let the engine
figure out the optimal strategy.
---
 .changes/unreleased/Under the Hood-20231003-161428.yaml | 7 +++++++
 dbt/include/trino/macros/catalog.sql                    | 7 +------
 2 files changed, 8 insertions(+), 6 deletions(-)
 create mode 100644 .changes/unreleased/Under the Hood-20231003-161428.yaml

diff --git a/.changes/unreleased/Under the Hood-20231003-161428.yaml b/.changes/unreleased/Under the Hood-20231003-161428.yaml
new file mode 100644
index 00000000..18c8413b
--- /dev/null
+++ b/.changes/unreleased/Under the Hood-20231003-161428.yaml	
@@ -0,0 +1,7 @@
+kind: Under the Hood
+body: Query table_comments without unrolling with UNION ALL
+time: 2023-10-03T16:14:28.238801+02:00
+custom:
+  Author: findepi
+  Issue: ""
+  PR: "357"
diff --git a/dbt/include/trino/macros/catalog.sql b/dbt/include/trino/macros/catalog.sql
index d7e252c3..f7c63283 100644
--- a/dbt/include/trino/macros/catalog.sql
+++ b/dbt/include/trino/macros/catalog.sql
@@ -67,7 +67,6 @@
 
 
 {% macro trino__get_catalog_table_comment_schemas_sql(information_schema, schemas) -%}
-    {%- for schema in schemas %}
     select
         catalog_name as "table_database",
         schema_name as "table_schema",
@@ -79,11 +78,7 @@
         and
         schema_name != 'information_schema'
         and
-        schema_name = '{{ schema | lower }}'
-    {%- if not loop.last %}
-    union all
-    {% endif -%}
-    {%- endfor -%}
+        schema_name in ('{{ schemas | join("','") | lower }}')
 {%- endmacro %}