Handle top spans with empty query string

Some functions will only store the query tree and no source in pg_proc. When those are called, the query text will be empty. We don't have information available from the hook so just skip setting an operation name.
DataDog · Apr 19, 2024 · 8ecd15a · 8ecd15a
1 parent db3b8f7
commit 8ecd15a
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diff --git a/expected/select.out b/expected/select.out
@@ -263,7 +263,6 @@ SELECT lazy_function('{1,2,3,4}'::int[]) FROM (VALUES (1,2)) as t;
              4
 (4 rows)
 
--- Check lazy function spans
 SELECT span_type, span_operation, parameters, lvl from peek_ordered_spans;
    span_type    |                                                                                             span_operation                                                                                              |            parameters            | lvl 
 ----------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+----------------------------------+-----
@@ -278,6 +277,31 @@ SELECT span_type, span_operation, parameters, lvl from peek_ordered_spans;
  Planner        | Planner                                                                                                                                                                                                 |                                  |   5
 (9 rows)
 
+CALL clean_spans();
+-- Check function calls that don't have sources in pg_proc
+SELECT information_schema._pg_truetypid(a, t) FROM pg_attribute a, pg_type t limit 1;
+ _pg_truetypid 
+---------------
+            26
+(1 row)
+
+SELECT span_type, span_operation, parameters, lvl from peek_ordered_spans;
+  span_type   |                                     span_operation                                     | parameters | lvl 
+--------------+----------------------------------------------------------------------------------------+------------+-----
+ Select query | SELECT information_schema._pg_truetypid(a, t) FROM pg_attribute a, pg_type t limit $1; | $1 = 1     |   1
+ Planner      | Planner                                                                                |            |   2
+ Executor     | ExecutorRun                                                                            |            |   2
+ Limit        | Limit                                                                                  |            |   3
+ NestedLoop   | NestedLoop                                                                             |            |   4
+ SeqScan      | SeqScan on pg_attribute a                                                              |            |   5
+ Materialize  | Materialize                                                                            |            |   5
+ SeqScan      | SeqScan on pg_type t                                                                   |            |   6
+ Select query | Top                                                                                    |            |   3
+ Planner      | Planner                                                                                |            |   4
+ Executor     | ExecutorRun                                                                            |            |   4
+ Result       | Result                                                                                 |            |   5
+(12 rows)
+
 -- Cleanup
 CALL clean_spans();
 CALL reset_settings();
diff --git a/sql/select.sql b/sql/select.sql
@@ -95,7 +95,11 @@ CREATE OR REPLACE FUNCTION lazy_function(IN anyarray, OUT x anyelement)
     LANGUAGE sql
     AS 'select * from pg_catalog.generate_series(array_lower($1, 1), array_upper($1, 1), 1)';
 SELECT lazy_function('{1,2,3,4}'::int[]) FROM (VALUES (1,2)) as t;
--- Check lazy function spans
+SELECT span_type, span_operation, parameters, lvl from peek_ordered_spans;
+CALL clean_spans();
+
+-- Check function calls that don't have sources in pg_proc
+SELECT information_schema._pg_truetypid(a, t) FROM pg_attribute a, pg_type t limit 1;
 SELECT span_type, span_operation, parameters, lvl from peek_ordered_spans;
 
 -- Cleanup

diff --git a/src/pg_tracing.c b/src/pg_tracing.c
@@ -1395,8 +1395,9 @@ begin_top_span(pgTracingTraceContext * trace_context, Span * top_span,
 		}
 		normalised_query = normalise_query(query_text, stmt_location, &query_len);
 	}
-	top_span->operation_name_offset = add_str_to_trace_buffer(normalised_query,
-															  query_len);
+    if (query_len > 0)
+        top_span->operation_name_offset = add_str_to_trace_buffer(normalised_query,
+                                                                  query_len);
 }
 
 /*