sql: add bytes_read metric

Add new `sql.statements.bytes_read.count` metric that counts the number of
bytes scanned by SQL statements. This is the same value that's collected by
SQL stats for each statement and transaction, except in aggregated metric
form.

Epic: AOP-30

Release note (sql change): Added sql.statements.bytes_read.count metric that
counts the number of bytes scanned by SQL statements.

Author: andy-kimball

docs/generated/metrics/metrics.yaml

@@ -8747,17 +8747,33 @@ layers:
       unit: COUNT
       aggregation: AVG
       derivative: NON_NEGATIVE_DERIVATIVE
+    - name: sql.statements.bytes_read.count
+      exported_name: sql_statements_bytes_read_count
+      description: Number of bytes read by SQL statements
+      y_axis_label: SQL Statements
+      type: COUNTER
+      unit: BYTES
+      aggregation: AVG
+      derivative: NON_NEGATIVE_DERIVATIVE
+    - name: sql.statements.bytes_read.count.internal
+      exported_name: sql_statements_bytes_read_count_internal
+      description: Number of bytes read by SQL statements (internal queries)
+      y_axis_label: SQL Internal Statements
+      type: COUNTER
+      unit: BYTES
+      aggregation: AVG
+      derivative: NON_NEGATIVE_DERIVATIVE
     - name: sql.statements.rows_read.count
       exported_name: sql_statements_rows_read_count
-      description: Number of rows read by SQL statements from primary and secondary indexes
+      description: Number of rows read by SQL statements
       y_axis_label: SQL Statements
       type: COUNTER
       unit: COUNT
       aggregation: AVG
       derivative: NON_NEGATIVE_DERIVATIVE
     - name: sql.statements.rows_read.count.internal
       exported_name: sql_statements_rows_read_count_internal
-      description: Number of rows read by SQL statements from primary and secondary indexes (internal queries)
+      description: Number of rows read by SQL statements (internal queries)
       y_axis_label: SQL Internal Statements
       type: COUNTER
       unit: COUNT

pkg/sql/conn_executor.go

@@ -626,6 +626,7 @@ func makeMetrics(internal bool, sv *settings.Values) Metrics {
 			TxnRetryCount:                     metric.NewCounter(getMetricMeta(MetaTxnRetry, internal)),
 			StatementRetryCount:               metric.NewCounter(getMetricMeta(MetaStatementRetry, internal)),
 			StatementRowsRead:                 metric.NewCounter(getMetricMeta(MetaStatementRowsRead, internal)),
+			StatementBytesRead:                metric.NewCounter(getMetricMeta(MetaStatementBytesRead, internal)),
 		},
 		StartedStatementCounters:  makeStartedStatementCounters(internal),
 		ExecutedStatementCounters: makeExecutedStatementCounters(internal),

pkg/sql/exec_util.go

@@ -1516,10 +1516,16 @@ var (
 	}
 	MetaStatementRowsRead = metric.Metadata{
 		Name:        "sql.statements.rows_read.count",
-		Help:        "Number of rows read by SQL statements from primary and secondary indexes",
+		Help:        "Number of rows read by SQL statements",
 		Measurement: "SQL Statements",
 		Unit:        metric.Unit_COUNT,
 	}
+	MetaStatementBytesRead = metric.Metadata{
+		Name:        "sql.statements.bytes_read.count",
+		Help:        "Number of bytes read by SQL statements",
+		Measurement: "SQL Statements",
+		Unit:        metric.Unit_BYTES,
+	}
 )
 
 func getMetricMeta(meta metric.Metadata, internal bool) metric.Metadata {

pkg/sql/executor_statement_metrics.go

@@ -88,6 +88,10 @@ type EngineMetrics struct {
 	// primary and secondary indexes. Note that some secondary indexes can have
 	// multiple index rows per primary index row (e.g. inverted and vector).
 	StatementRowsRead *metric.Counter
+
+	// StatementBytesRead counts the number of bytes scanned by SQL statements
+	// from primary and secondary indexes.
+	StatementBytesRead *metric.Counter
 }
 
 // EngineMetrics implements the metric.Struct interface.
@@ -204,6 +208,7 @@ func (ex *connExecutor) recordStatementSummary(
 
 	// Update SQL statement metrics.
 	ex.metrics.EngineMetrics.StatementRowsRead.Inc(stats.rowsRead)
+	ex.metrics.EngineMetrics.StatementBytesRead.Inc(stats.bytesRead)
 
 	if ex.statsCollector.EnabledForTransaction() {
 		recordedStmtStats := &sqlstats.RecordedStmtStats{

pkg/sql/metric_test.go

@@ -246,8 +246,6 @@ func TestStatementMetrics(t *testing.T) {
 		{query: `SELECT * FROM db.t ORDER BY v <-> '[2, 2]' LIMIT 1`, rowsRead: 3},
 	}
 
-	lastRowsRead := s.MustGetSQLCounter(sql.MetaStatementRowsRead.Name)
-
 	for _, tc := range testCases {
 		t.Run(tc.query, func(t *testing.T) {
 			for _, vectorized := range []string{"off", "on"} {
@@ -257,11 +255,23 @@ func TestStatementMetrics(t *testing.T) {
 						return
 					}
 
+					// Get initial values of the counters.
+					lastRowsRead := s.MustGetSQLCounter(sql.MetaStatementRowsRead.Name)
+					lastBytesRead := s.MustGetSQLCounter(sql.MetaStatementBytesRead.Name)
+
 					runner.Exec(t, tc.query)
+
+					// Test the rows read metric.
 					actual, err := checkCounterDelta(
 						s, sql.MetaStatementRowsRead, lastRowsRead, tc.rowsRead)
 					require.NoError(t, err)
 					lastRowsRead = actual
+
+					// If there were rows read, then expect bytes read to have
+					// increased. Don't check for a specific value, since there are
+					// too many factors that can change this.
+					currBytesRead := s.MustGetSQLCounter(sql.MetaStatementBytesRead.Name)
+					require.Greater(t, currBytesRead, lastBytesRead)
 				})
 			}
 		})