feat: Add clickhouse dialect (#1090)

* feat: Add clickhouse dialect

Author: max-sixty

prql-compiler/src/ast/dialect.rs

@@ -38,6 +38,7 @@ impl Dialect {
             Dialect::MsSql => Box::new(MsSqlDialect),
             Dialect::MySql => Box::new(MySqlDialect),
             Dialect::BigQuery => Box::new(BigQueryDialect),
+            Dialect::ClickHouse => Box::new(ClickHouseDialect),
             _ => Box::new(GenericDialect),
         }
     }
@@ -53,6 +54,7 @@ pub struct GenericDialect;
 pub struct MySqlDialect;
 pub struct MsSqlDialect;
 pub struct BigQueryDialect;
+pub struct ClickHouseDialect;
 
 pub trait DialectHandler {
     fn dialect(&self) -> Dialect;
@@ -89,6 +91,15 @@ impl DialectHandler for MySqlDialect {
     }
 }
 
+impl DialectHandler for ClickHouseDialect {
+    fn dialect(&self) -> Dialect {
+        Dialect::ClickHouse
+    }
+    fn ident_quote(&self) -> char {
+        '`'
+    }
+}
+
 impl DialectHandler for BigQueryDialect {
     fn dialect(&self) -> Dialect {
         Dialect::BigQuery

prql-compiler/src/lib.rs

@@ -1475,6 +1475,24 @@ take 20
         "###);
     }
 
+    #[test]
+    fn test_dialect_clickhouse() {
+        let query = r###"
+        prql dialect:clickhouse
+
+        from github_json
+        derive [event_type_dotted = `event.type`]
+        "###;
+
+        assert_display_snapshot!((compile(query).unwrap()), @r###"
+        SELECT
+          github_json.*,
+          github_json.`event.type` AS event_type_dotted
+        FROM
+          github_json
+        "###);
+    }
+
     #[test]
     #[ignore]
     fn test_ident_escaping() {