sql: SHOW QUERIES lazily interpolate placeholders

SHOW QUERIES (and crdb_internal.node_queries, cluster_queries)
interpolates placeholder values into the statement so that it is
possible to see the placeholder values of a prepared statement - but it
used to do this unconditionally during statement execution.

This is an expensive process that spends a lot of CPU for little reason,
since the interpolation was happening in the hot path of every query.

Now, we include the placeholder values as a separate array in the
internal representation of active queries, and interpolate the values
only when they're being pulled out to examine, to avoid the
unconditional runtime interpolation costs.

As a side effect of this change, the original comments in a query are
now included in SHOW QUERIES and the two active queries tables.

Release note (sql change): the query field in the
crdb_internal.node_queries, crdb_internal.cluster_queries, and SHOW
QUERIES commands no longer interpolates placeholders. The placeholders
are now included as a SQL text array in the new placeholders column of
those tables. Comments from queries are also now included in the
aforementioned query tables.

docs/generated/http/full.md

@@ -2140,6 +2140,7 @@ ActiveQuery represents a query in flight on some Session.
 | is_full_scan | [bool](#cockroach.server.serverpb.ListSessionsResponse-bool) |  | True if the query contains a full table or index scan. Note that this field is only valid if the query is in the EXECUTING phase. | [reserved](#support-status) |
 | elapsed_time | [google.protobuf.Duration](#cockroach.server.serverpb.ListSessionsResponse-google.protobuf.Duration) |  | Time elapsed since this query started execution. | [reserved](#support-status) |
 | plan_gist | [string](#cockroach.server.serverpb.ListSessionsResponse-string) |  | The compressed plan that can be converted back into the statement's logical plan. Empty if the statement is in the PREPARING state. | [reserved](#support-status) |
+| placeholders | [string](#cockroach.server.serverpb.ListSessionsResponse-string) | repeated | The placeholders if any. | [reserved](#support-status) |
 
 
 
@@ -2283,6 +2284,7 @@ ActiveQuery represents a query in flight on some Session.
 | is_full_scan | [bool](#cockroach.server.serverpb.ListSessionsResponse-bool) |  | True if the query contains a full table or index scan. Note that this field is only valid if the query is in the EXECUTING phase. | [reserved](#support-status) |
 | elapsed_time | [google.protobuf.Duration](#cockroach.server.serverpb.ListSessionsResponse-google.protobuf.Duration) |  | Time elapsed since this query started execution. | [reserved](#support-status) |
 | plan_gist | [string](#cockroach.server.serverpb.ListSessionsResponse-string) |  | The compressed plan that can be converted back into the statement's logical plan. Empty if the statement is in the PREPARING state. | [reserved](#support-status) |
+| placeholders | [string](#cockroach.server.serverpb.ListSessionsResponse-string) | repeated | The placeholders if any. | [reserved](#support-status) |
 
 
 

pkg/server/serverpb/status.proto

@@ -916,6 +916,10 @@ message ActiveQuery {
   // The compressed plan that can be converted back into the statement's logical plan.
   // Empty if the statement is in the PREPARING state.
   string plan_gist = 12;
+
+  // The placeholders if any.
+  repeated string placeholders = 13;
+
 }
 
 // Request object for ListSessions and ListLocalSessions.

pkg/sql/conn_executor.go

@@ -3176,12 +3176,16 @@ func (ex *connExecutor) serialize() serverpb.Session {
 		if query.hidden {
 			continue
 		}
-		ast, err := query.getStatement()
-		if err != nil {
-			continue
+		sqlNoConstants := truncateSQL(formatStatementHideConstants(query.stmt.AST))
+		nPlaceholders := 0
+		if query.placeholders != nil {
+			nPlaceholders = len(query.placeholders.Values)
+		}
+		placeholders := make([]string, nPlaceholders)
+		for i := range placeholders {
+			placeholders[i] = tree.AsStringWithFlags(query.placeholders.Values[i], tree.FmtSimple)
 		}
-		sqlNoConstants := truncateSQL(formatStatementHideConstants(ast))
-		sql := truncateSQL(ast.String())
+		sql := truncateSQL(query.stmt.SQL)
 		progress := math.Float64frombits(atomic.LoadUint64(&query.progressAtomic))
 		queryStart := query.start.UTC()
 		activeQueries = append(activeQueries, serverpb.ActiveQuery{
@@ -3191,7 +3195,8 @@ func (ex *connExecutor) serialize() serverpb.Session {
 			ElapsedTime:    timeNow.Sub(queryStart),
 			Sql:            sql,
 			SqlNoConstants: sqlNoConstants,
-			SqlSummary:     formatStatementSummary(ast),
+			SqlSummary:     formatStatementSummary(query.stmt.AST),
+			Placeholders:   placeholders,
 			IsDistributed:  query.isDistributed,
 			Phase:          (serverpb.ActiveQuery_Phase)(query.phase),
 			Progress:       float32(progress),

pkg/sql/conn_executor_exec.go

@@ -307,15 +307,9 @@ func (ex *connExecutor) execStmtInOpenState(
 	var queryDoneAfterFunc chan struct{}
 	var txnDoneAfterFunc chan struct{}
 
-	// Early-associate placeholder info with the eval context,
-	// so that we can fill in placeholder values in our call to addActiveQuery, below.
-	if !ex.planner.EvalContext().HasPlaceholders() {
-		ex.planner.EvalContext().Placeholders = pinfo
-	}
-
 	var cancelQuery context.CancelFunc
 	ctx, cancelQuery = contextutil.WithCancel(ctx)
-	ex.addActiveQuery(ast, formatWithPlaceholders(ctx, ast, ex.planner.EvalContext()), queryID, cancelQuery)
+	ex.addActiveQuery(parserStmt, pinfo, queryID, cancelQuery)
 
 	// Make sure that we always unregister the query. It also deals with
 	// overwriting res.Error to a more user-friendly message in case of query
@@ -547,7 +541,7 @@ func (ex *connExecutor) execStmtInOpenState(
 			if perr, ok := retPayload.(payloadWithError); ok {
 				execErr = perr.errorCause()
 			}
-			filter(ctx, ex.sessionData(), ast.String(), execErr)
+			filter(ctx, ex.sessionData(), stmt.AST.String(), execErr)
 		}
 
 		// Do the auto-commit, if necessary. In the extended protocol, the
@@ -2106,13 +2100,17 @@ func (ex *connExecutor) enableTracing(modes []string) error {
 
 // addActiveQuery adds a running query to the list of running queries.
 func (ex *connExecutor) addActiveQuery(
-	ast tree.Statement, rawStmt string, queryID clusterunique.ID, cancelQuery context.CancelFunc,
+	stmt parser.Statement,
+	placeholders *tree.PlaceholderInfo,
+	queryID clusterunique.ID,
+	cancelQuery context.CancelFunc,
 ) {
-	_, hidden := ast.(tree.HiddenFromShowQueries)
+	_, hidden := stmt.AST.(tree.HiddenFromShowQueries)
 	qm := &queryMeta{
 		txnID:         ex.state.mu.txn.ID(),
 		start:         ex.phaseTimes.GetSessionPhaseTime(sessionphase.SessionQueryReceived),
-		rawStmt:       rawStmt,
+		stmt:          stmt,
+		placeholders:  placeholders,
 		phase:         preparing,
 		isDistributed: false,
 		isFullScan:    false,

pkg/sql/crdb_internal.go

@@ -53,6 +53,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/sql/catalog/tabledesc"
 	"github.com/cockroachdb/cockroach/pkg/sql/clusterunique"
 	"github.com/cockroachdb/cockroach/pkg/sql/idxusage"
+	"github.com/cockroachdb/cockroach/pkg/sql/parser"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgcode"
 	"github.com/cockroachdb/cockroach/pkg/sql/pgwire/pgerror"
 	"github.com/cockroachdb/cockroach/pkg/sql/privilege"
@@ -1902,14 +1903,16 @@ func populateQueriesTable(
 				planGistDatum = tree.NewDString(query.PlanGist)
 			}
 
+			// Interpolate placeholders into the SQL statement.
+			sql := formatActiveQuery(query)
 			if err := addRow(
 				tree.NewDString(query.ID),
 				txnID,
 				tree.NewDInt(tree.DInt(session.NodeID)),
 				sessionID,
 				tree.NewDString(session.Username),
 				ts,
-				tree.NewDString(query.Sql),
+				tree.NewDString(sql),
 				tree.NewDString(session.ClientAddress),
 				tree.NewDString(session.ApplicationName),
 				isDistributedDatum,
@@ -1949,6 +1952,33 @@ func populateQueriesTable(
 	return nil
 }
 
+// formatActiveQuery formats a serverpb.ActiveQuery by interpolating its
+// placeholders within the string.
+func formatActiveQuery(query serverpb.ActiveQuery) string {
+	parsed, parseErr := parser.ParseOne(query.Sql)
+	if parseErr != nil {
+		// If we failed to interpolate, rather than give up just send out the
+		// SQL without interpolated placeholders. Hallelujah!
+		return query.Sql
+	}
+	var sb strings.Builder
+	sql := tree.AsStringWithFlags(parsed.AST, tree.FmtSimple,
+		tree.FmtPlaceholderFormat(func(ctx *tree.FmtCtx, p *tree.Placeholder) {
+			if int(p.Idx) > len(query.Placeholders) {
+				ctx.Printf("$%d", p.Idx+1)
+				return
+			}
+			ctx.Printf(query.Placeholders[p.Idx])
+		}),
+	)
+	sb.WriteString(sql)
+	for i := range parsed.Comments {
+		sb.WriteString(" ")
+		sb.WriteString(parsed.Comments[i])
+	}
+	return sb.String()
+}
+
 const sessionsSchemaPattern = `
 CREATE TABLE crdb_internal.%s (
   node_id            INT NOT NULL,   -- the node on which the query is running
@@ -2019,7 +2049,8 @@ func populateSessionsTable(
 			// The array is leftover from a time when we allowed multiple
 			// queries to be executed at once in a session.
 			activeQueryStart = query.Start
-			activeQueries.WriteString(query.Sql)
+			sql := formatActiveQuery(query)
+			activeQueries.WriteString(sql)
 		}
 
 		var err error

pkg/sql/exec_util.go

@@ -1928,10 +1928,11 @@ type queryMeta struct {
 	// The timestamp when this query began execution.
 	start time.Time
 
-	// The string of the SQL statement being executed. This string may
-	// contain sensitive information, so it must be converted back into
-	// an AST and dumped before use in logging.
-	rawStmt string
+	// The SQL statement being executed.
+	stmt parser.Statement
+
+	// The placeholders that the query was executed with if any.
+	placeholders *tree.PlaceholderInfo
 
 	// States whether this query is distributed. Note that all queries,
 	// including those that are distributed, have this field set to false until
@@ -1970,16 +1971,6 @@ func (q *queryMeta) cancel() {
 	q.cancelQuery()
 }
 
-// getStatement returns a cleaned version of the query associated
-// with this queryMeta.
-func (q *queryMeta) getStatement() (tree.Statement, error) {
-	parsed, err := parser.ParseOne(q.rawStmt)
-	if err != nil {
-		return nil, err
-	}
-	return parsed.AST, nil
-}
-
 // SessionDefaults mirrors fields in Session, for restoring default
 // configuration values in SET ... TO DEFAULT (or RESET ...) statements.
 type SessionDefaults map[string]string

pkg/sql/show_test.go

@@ -726,6 +726,16 @@ func TestShowQueriesFillsInValuesForPlaceholders(t *testing.T) {
 			[]interface{}{"hello"},
 			"SELECT upper('hello')",
 		},
+		{
+			"SELECT /* test */ upper($1)",
+			[]interface{}{"hello"},
+			"SELECT upper('hello') /* test */",
+		},
+		{
+			"SELECT /* test */ 'hi'::string",
+			[]interface{}{},
+			"SELECT 'hi'::STRING /* test */",
+		},
 	}
 
 	// Perform both as a simple execution and as a prepared statement,
@@ -761,7 +771,14 @@ func TestShowQueriesFillsInValuesForPlaceholders(t *testing.T) {
 					t.Fatal(err)
 				}
 
-				require.Equal(t, test.expected, recordedQueries[test.statement])
+				// parse and stringify the statement so that it matches the key in the
+				// recordedQueries map.
+				stmt, err := parser.ParseOne(test.statement)
+				if err != nil {
+					t.Fatal(err)
+				}
+				sql := stmt.AST.String()
+				require.Equal(t, test.expected, recordedQueries[sql])
 			})
 		}
 	}