[release-17.0] Improve performance for BaseShowTablesWithSizes quer…

…y. (#15713) (#15792)

Signed-off-by: Arthur Schreiber <arthurschreiber@github.com>
Co-authored-by: Arthur Schreiber <arthurschreiber@github.com>
Co-authored-by: Deepthi Sigireddi <deepthi@planetscale.com>

go/mysql/flavor_mysql.go

@@ -342,41 +342,25 @@ GROUP BY t.table_name, t.table_type, t.create_time, t.table_comment`
 
 // TablesWithSize80 is a query to select table along with size for mysql 8.0
 //
-// We join with a subquery that materializes the data from `information_schema.innodb_sys_tablespaces`
-// early for performance reasons. This effectively causes only a single read of `information_schema.innodb_tablespaces`
-// per query.
 // Note the following:
-// - We use UNION ALL to deal differently with partitioned tables vs. non-partitioned tables.
-// Originally, the query handled both, but that introduced "WHERE ... OR" conditions that led to poor query
-// optimization. By separating to UNION ALL we remove all "OR" conditions.
+// - We use a single query to fetch both partitioned and non-partitioned tables. This is because
+// accessing `information_schema.innodb_tablespaces` is expensive on servers with many tablespaces,
+// and every query that loads the table needs to perform full table scans on it. Doing a single
+// table scan is more efficient than doing more than one.
 // - We utilize `INFORMATION_SCHEMA`.`TABLES`.`CREATE_OPTIONS` column to do early pruning before the JOIN.
 // - `TABLES`.`TABLE_NAME` has `utf8mb4_0900_ai_ci` collation. `INNODB_TABLESPACES`.`NAME` has `utf8mb3_general_ci`.
 // We normalize the collation to get better query performance (we force the casting at the time of our choosing)
-// - `create_options` is NULL for views, and therefore we need an additional UNION ALL to include views
 const TablesWithSize80 = `SELECT t.table_name,
- t.table_type,
- UNIX_TIMESTAMP(t.create_time),
- t.table_comment,
- i.file_size,
- i.allocated_size
- FROM information_schema.tables t
- LEFT JOIN information_schema.innodb_tablespaces i
- ON i.name = CONCAT(t.table_schema, '/', t.table_name) COLLATE utf8_general_ci
- WHERE
- t.table_schema = database() AND not t.create_options <=> 'partitioned'
-UNION ALL
- SELECT
- t.table_name,
  t.table_type,
  UNIX_TIMESTAMP(t.create_time),
  t.table_comment,
  SUM(i.file_size),
  SUM(i.allocated_size)
  FROM information_schema.tables t
  LEFT JOIN information_schema.innodb_tablespaces i
- ON i.name LIKE (CONCAT(t.table_schema, '/', t.table_name, '#p#%') COLLATE utf8_general_ci )
+ ON i.name LIKE CONCAT(t.table_schema, '/', t.table_name, IF(t.create_options <=> 'partitioned', '#p#%', '')) COLLATE utf8_general_ci
  WHERE
- t.table_schema = database() AND t.create_options <=> 'partitioned'
+ t.table_schema = database()
  GROUP BY
  t.table_schema, t.table_name, t.table_type, t.create_time, t.table_comment
 `

go/vt/vttablet/endtoend/misc_test.go

@@ -42,6 +42,7 @@ import (
  querypb "vitess.io/vitess/go/vt/proto/query"
  vtrpcpb "vitess.io/vitess/go/vt/proto/vtrpc"
  "vitess.io/vitess/go/vt/sqlparser"
+ "vitess.io/vitess/go/vt/vtgate/evalengine"
  "vitess.io/vitess/go/vt/vttablet/endtoend/framework"
 )
 
@@ -971,26 +972,89 @@ func TestShowTablesWithSizes(t *testing.T) {
  _, err := conn.ExecuteFetch(query, 1, false)
  require.NoError(t, err)
  }
- expectTables := map[string]([]string){ // TABLE_TYPE, TABLE_COMMENT
- "show_tables_with_sizes_t1": {"BASE TABLE", ""},
- "show_tables_with_sizes_v1": {"VIEW", "VIEW"},
- "show_tables_with_sizes_employees": {"BASE TABLE", ""},
+
+ expectedTables := []string{
+ "show_tables_with_sizes_t1",
+ "show_tables_with_sizes_v1",
+ "show_tables_with_sizes_employees",
  }
+ actualTables := []string{}
 
  rs, err := conn.ExecuteFetch(conn.BaseShowTablesWithSizes(), math.MaxInt, false)
  require.NoError(t, err)
  require.NotEmpty(t, rs.Rows)
 
- assert.GreaterOrEqual(t, len(rs.Rows), len(expectTables))
- matchedTables := map[string]bool{}
+ assert.GreaterOrEqual(t, len(rs.Rows), len(expectedTables))
+
  for _, row := range rs.Rows {
+ assert.Equal(t, 6, len(row))
+
  tableName := row[0].ToString()
- vals, ok := expectTables[tableName]
- if ok {
- assert.Equal(t, vals[0], row[1].ToString()) // TABLE_TYPE
- assert.Equal(t, vals[1], row[3].ToString()) // TABLE_COMMENT
- matchedTables[tableName] = true
+ if tableName == "show_tables_with_sizes_t1" {
+ // TABLE_TYPE
+ assert.Equal(t, "BASE TABLE", row[1].ToString())
+
+ assert.True(t, row[2].IsIntegral())
+ createTime, err := evalengine.ToInt64(row[2])
+ assert.NoError(t, err)
+ assert.Greater(t, createTime, int64(0))
+
+ // TABLE_COMMENT
+ assert.Equal(t, "", row[3].ToString())
+
+ assert.True(t, row[4].IsDecimal())
+ fileSize, err := evalengine.ToInt64(row[4])
+ assert.NoError(t, err)
+ assert.Greater(t, fileSize, int64(0))
+
+ assert.True(t, row[4].IsDecimal())
+ allocatedSize, err := evalengine.ToInt64(row[5])
+ assert.NoError(t, err)
+ assert.Greater(t, allocatedSize, int64(0))
+
+ actualTables = append(actualTables, tableName)
+ } else if tableName == "show_tables_with_sizes_v1" {
+ // TABLE_TYPE
+ assert.Equal(t, "VIEW", row[1].ToString())
+
+ assert.True(t, row[2].IsIntegral())
+ createTime, err := evalengine.ToInt64(row[2])
+ assert.NoError(t, err)
+ assert.Greater(t, createTime, int64(0))
+
+ // TABLE_COMMENT
+ assert.Equal(t, "VIEW", row[3].ToString())
+
+ assert.True(t, row[4].IsNull())
+ assert.True(t, row[5].IsNull())
+
+ actualTables = append(actualTables, tableName)
+ } else if tableName == "show_tables_with_sizes_employees" {
+ // TABLE_TYPE
+ assert.Equal(t, "BASE TABLE", row[1].ToString())
+
+ assert.True(t, row[2].IsIntegral())
+ createTime, err := evalengine.ToInt64(row[2])
+ assert.NoError(t, err)
+ assert.Greater(t, createTime, int64(0))
+
+ // TABLE_COMMENT
+ assert.Equal(t, "", row[3].ToString())
+
+ assert.True(t, row[4].IsDecimal())
+ fileSize, err := evalengine.ToInt64(row[4])
+ assert.NoError(t, err)
+ assert.Greater(t, fileSize, int64(0))
+
+ assert.True(t, row[5].IsDecimal())
+ allocatedSize, err := evalengine.ToInt64(row[5])
+ assert.NoError(t, err)
+ assert.Greater(t, allocatedSize, int64(0))
+
+ actualTables = append(actualTables, tableName)
  }
  }
- assert.Equalf(t, len(expectTables), len(matchedTables), "%v", matchedTables)
+
+ assert.Equal(t, len(expectedTables), len(actualTables))
+ assert.ElementsMatch(t, expectedTables, actualTables)
 }