Runtime: Add missing dry run support in Exec method of clickhouse d…

…river (#4559)

* dry run exec support clickhouse

* fix and unit test

* use explain for dry run

runtime/drivers/clickhouse/information_schema_test.go

@@ -152,8 +152,21 @@ func prepareConn(t *testing.T, conn drivers.Handle) {
 	})
 	require.NoError(t, err)
 
+	// test dry run
 	err = olap.Exec(context.Background(), &drivers.Statement{
-		Query: "INSERT INTO other.bar VALUES ('a', 1), ('a', 2), ('b', 3), ('c', 4)",
+		DryRun: true,
+		Query: `WITH cte_numbers AS
+			(
+				SELECT num
+				FROM generateRandom('num UInt64', NULL)
+				LIMIT 10000000000
+			)
+		SELECT count()
+		FROM cte_numbers
+		WHERE num IN (
+			SELECT num
+			FROM cte_numbers
+		)`,
 	})
 	require.NoError(t, err)
 }

runtime/drivers/clickhouse/olap.go

@@ -7,7 +7,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/google/uuid"
 	"github.com/jmoiron/sqlx"
 	runtimev1 "github.com/rilldata/rill/proto/gen/rill/runtime/v1"
 	"github.com/rilldata/rill/runtime/drivers"
@@ -60,6 +59,18 @@ func (c *connection) Exec(ctx context.Context, stmt *drivers.Statement) error {
 		c.logger.Info("clickhouse query", zap.String("sql", stmt.Query), zap.Any("args", stmt.Args))
 	}
 
+	// We use the meta conn for dry run queries
+	if stmt.DryRun {
+		conn, release, err := c.acquireMetaConn(ctx)
+		if err != nil {
+			return err
+		}
+		defer func() { _ = release() }()
+
+		_, err = conn.ExecContext(ctx, fmt.Sprintf("EXPLAIN %s", stmt.Query), stmt.Args...)
+		return err
+	}
+
 	conn, release, err := c.acquireOLAPConn(ctx, stmt.Priority)
 	if err != nil {
 		return err
@@ -94,15 +105,7 @@ func (c *connection) Execute(ctx context.Context, stmt *drivers.Statement) (res
 		}
 		defer func() { _ = release() }()
 
-		// TODO: Find way to validate with args
-
-		name := uuid.NewString()
-		_, err = conn.ExecContext(ctx, fmt.Sprintf("CREATE TEMPORARY VIEW %q AS %s", name, stmt.Query))
-		if err != nil {
-			return nil, err
-		}
-
-		_, err = conn.ExecContext(context.Background(), fmt.Sprintf("DROP VIEW %q", name))
+		_, err = conn.ExecContext(ctx, fmt.Sprintf("EXPLAIN %s", stmt.Query), stmt.Args...)
 		return nil, err
 	}