Handle current_setting parameters with empty strings in insert_event_log

PR-URL: hasura/graphql-engine-mono#11143
GitOrigin-RevId: a04c8c9d04557817a1249de78ef5c6f915d3e706

server/src-lib/Hasura/Backends/Postgres/DDL/Source/Version.hs

@@ -27,7 +27,7 @@ initialSourceCatalogVersion :: SourceCatalogVersion pgKind
 initialSourceCatalogVersion = Version.SourceCatalogVersion 0
 
 latestSourceCatalogVersion :: SourceCatalogVersion pgKind
-latestSourceCatalogVersion = Version.SourceCatalogVersion 3
+latestSourceCatalogVersion = Version.SourceCatalogVersion 4
 
 previousSourceCatalogVersions :: [SourceCatalogVersion pgKind]
 previousSourceCatalogVersions = [initialSourceCatalogVersion .. pred latestSourceCatalogVersion]

server/src-rsr/init_pg_source.sql

@@ -88,8 +88,11 @@ CREATE OR REPLACE FUNCTION
     id := gen_random_uuid();
     server_version_num := current_setting('server_version_num');
     IF server_version_num >= 90600 THEN
-      session_variables := current_setting('hasura.user', 't');
-      trace_context := current_setting('hasura.tracecontext', 't');
+      -- In some cases postgres sets the setting to an empty string, which is not a valid json.
+      -- NULLIF will convert the empty string to NULL.
+      -- Ref: https://github.com/hasura/graphql-engine/issues/8498
+      session_variables := NULLIF(current_setting('hasura.user', 't'), '');
+      trace_context := NULLIF(current_setting('hasura.tracecontext', 't'), '');
     ELSE
       BEGIN
         session_variables := current_setting('hasura.user');

server/src-rsr/pg_source_migrations/3_to_4.sql

@@ -0,0 +1,43 @@
+CREATE OR REPLACE FUNCTION
+  hdb_catalog.insert_event_log(schema_name text, table_name text, trigger_name text, op text, row_data json)
+  RETURNS text AS $$
+  DECLARE
+    id text;
+    payload json;
+    session_variables json;
+    server_version_num int;
+    trace_context json;
+  BEGIN
+    id := gen_random_uuid();
+    server_version_num := current_setting('server_version_num');
+    IF server_version_num >= 90600 THEN
+      -- In some cases postgres sets the setting to an empty string, which is not a valid json.
+      -- NULLIF will convert the empty string to NULL.
+      -- Ref: https://github.com/hasura/graphql-engine/issues/8498
+      session_variables := NULLIF(current_setting('hasura.user', 't'), '');
+      trace_context := NULLIF(current_setting('hasura.tracecontext', 't'), '');
+    ELSE
+      BEGIN
+        session_variables := current_setting('hasura.user');
+      EXCEPTION WHEN OTHERS THEN
+                  session_variables := NULL;
+      END;
+      BEGIN
+        trace_context := current_setting('hasura.tracecontext');
+      EXCEPTION WHEN OTHERS THEN
+        trace_context := NULL;
+      END;
+    END IF;
+    payload := json_build_object(
+      'op', op,
+      'data', row_data,
+      'session_variables', session_variables,
+      'trace_context', trace_context
+    );
+    INSERT INTO hdb_catalog.event_log
+                (id, schema_name, table_name, trigger_name, payload)
+    VALUES
+    (id, schema_name, table_name, trigger_name, payload);
+    RETURN id;
+  END;
+$$ LANGUAGE plpgsql;