workload: enhance querybench

Release justification: non-production code changes.

`querybench` workload has been enhanced to support queries that consist
of multiple statements that are present on a single line. Previously,
the workload would fail on such queries because it attempts to `Prepare`
the whole line which would error out. Now we're still attempting to
prepare the whole line, but if that fails, we will store plain query and
will be executing it using `DB.Query` rather that `Stmt.Query`.

Release note: None

pkg/workload/querybench/query_bench.go

@@ -134,16 +134,17 @@ func (g *queryBench) Ops(urls []string, reg *histogram.Registry) (workload.Query
 
 	stmts := make([]namedStmt, len(g.queries))
 	for i, query := range g.queries {
-		stmt, err := db.Prepare(query)
-		if err != nil {
-			return workload.QueryLoad{}, errors.Wrapf(err, "failed to prepare query %q", query)
-		}
 		stmts[i] = namedStmt{
 			// TODO(solon): Allow specifying names in the query file rather than using
 			// the entire query as the name.
 			name: fmt.Sprintf("%2d: %s", i+1, query),
-			stmt: stmt,
 		}
+		stmt, err := db.Prepare(query)
+		if err != nil {
+			stmts[i].query = query
+			continue
+		}
+		stmts[i].preparedStmt = stmt
 	}
 
 	maxNumStmts := 0
@@ -192,7 +193,11 @@ func GetQueries(path string) ([]string, error) {
 
 type namedStmt struct {
 	name string
-	stmt *gosql.Stmt
+	// We will try to Prepare the statement, and if that succeeds, the prepared
+	// statement will be stored in `preparedStmt', otherwise, we will store
+	// plain query in 'query'.
+	preparedStmt *gosql.Stmt
+	query        string
 }
 
 type queryBenchWorker struct {
@@ -221,15 +226,31 @@ func (o *queryBenchWorker) run(ctx context.Context) error {
 	stmt := o.stmts[o.stmtIdx%len(o.stmts)]
 	o.stmtIdx++
 
-	rows, err := stmt.stmt.Query()
-	if err != nil {
-		return err
-	}
-	defer rows.Close()
-	for rows.Next() {
+	exhaustRows := func(execFn func() (*gosql.Rows, error)) error {
+		rows, err := execFn()
+		if err != nil {
+			return err
+		}
+		defer rows.Close()
+		for rows.Next() {
+		}
+		if err := rows.Err(); err != nil {
+			return err
+		}
+		return nil
 	}
-	if err := rows.Err(); err != nil {
-		return err
+	if stmt.preparedStmt != nil {
+		if err := exhaustRows(func() (*gosql.Rows, error) {
+			return stmt.preparedStmt.Query()
+		}); err != nil {
+			return err
+		}
+	} else {
+		if err := exhaustRows(func() (*gosql.Rows, error) {
+			return o.db.Query(stmt.query)
+		}); err != nil {
+			return err
+		}
 	}
 	elapsed := timeutil.Since(start)
 	if o.verbose {

pkg/workload/querybench/tpch-queries

@@ -44,9 +44,7 @@ SELECT c_count, count(*) AS custdist FROM ( SELECT c_custkey, count(o_orderkey)
 SELECT 100.00 * sum(CASE WHEN p_type LIKE 'PROMO%' THEN l_extendedprice * (1 - l_discount) ELSE 0 END) / sum(l_extendedprice * (1 - l_discount)) AS promo_revenue FROM lineitem, part WHERE l_partkey = p_partkey AND l_shipdate >= DATE '1995-09-01' AND l_shipdate < DATE '1995-09-01' + INTERVAL '1' MONTH
 
 -- query 15
-CREATE VIEW revenue0 (supplier_no, total_revenue) AS SELECT l_suppkey, sum(l_extendedprice * (1 - l_discount)) FROM lineitem WHERE l_shipdate >= DATE '1996-01-01' AND l_shipdate < DATE '1996-01-01' + INTERVAL '3' MONTH GROUP BY l_suppkey
-SELECT s_suppkey, s_name, s_address, s_phone, total_revenue FROM supplier, revenue0 WHERE s_suppkey = supplier_no AND total_revenue = ( SELECT max(total_revenue) FROM revenue0) ORDER BY s_suppkey
-DROP VIEW revenue0
+CREATE VIEW revenue0 (supplier_no, total_revenue) AS SELECT l_suppkey, sum(l_extendedprice * (1 - l_discount)) FROM lineitem WHERE l_shipdate >= DATE '1996-01-01' AND l_shipdate < DATE '1996-01-01' + INTERVAL '3' MONTH GROUP BY l_suppkey; SELECT s_suppkey, s_name, s_address, s_phone, total_revenue FROM supplier, revenue0 WHERE s_suppkey = supplier_no AND total_revenue = ( SELECT max(total_revenue) FROM revenue0) ORDER BY s_suppkey; DROP VIEW revenue0
 
 -- query 16
 SELECT p_brand, p_type, p_size, count(distinct ps_suppkey) AS supplier_cnt FROM partsupp, part WHERE p_partkey = ps_partkey AND p_brand <> 'Brand#45' AND p_type NOT LIKE 'MEDIUM POLISHED%' AND p_size IN (49, 14, 23, 45, 19, 3, 36, 9) AND ps_suppkey NOT IN ( SELECT s_suppkey FROM supplier WHERE s_comment LIKE '%Customer%Complaints%') GROUP BY p_brand, p_type, p_size ORDER BY supplier_cnt DESC, p_brand, p_type, p_size