On Sat, Dec 21, 2019 at 04:25:05PM -0500, Tom Lane wrote:
Nikolay Samokhvalov <samokhva...@gmail.com> writes:Here is what ORMs do: select length('SELECT "column_name_1001", "column_name_1002", "column_name_1003", "column_name_1004", "column_name_1005", "column_name_1006", "column_name_1007", "column_name_1008", "column_name_1009", "column_name_1010", "column_name_1011", "column_name_1012", "column_name_1013", "column_name_1014", "column_name_1015", "column_name_1016", "column_name_1017", "column_name_1018", "column_name_1019", "column_name_1020", "column_name_1021", "column_name_1022", "column_name_1023", "column_name_1024", "column_name_1025", "column_name_1026", "column_name_1027", "column_name_1028", "column_name_1029", "column_name_1030", "column_name_1031", "column_name_1032", "column_name_1033", "column_name_1034", "column_name_1035", "column_name_1036", "column_name_1037", "column_name_1038", "column_name_1039", "column_name_1040", "column_name_1041", "column_name_1042", "column_name_1043", "column_name_1044", "column_name_1045", "column_name_1046", "column_name_1047", "column_name_1048", "column_name_1049", "column_name_1050" FROM "some_table";'); length -------- 1024 (1 row)That's it – with default settings, you won't see WHERE clause or anything else.If that's true, it doesn't offer much of a case for upping the limit on track_activity_query_size. The longest such a query could reasonably get is somewhere near NAMEDATALEN times MaxHeapAttributeNumber, which as it happens is exactly the existing limit on track_activity_query_size.As a result, many queries exceed track_activity_query_sizeHow? And if they are, why do you care? Such queries sure seem pretty content-free.
I believe the example was just a very simplistic example. ORMs can of course generate queries with joins, which can easily exceed the limit you mentioned.
What is the overhead here except the memory consumption?The time to copy those strings out of shared storage, any time you query pg_stat_activity.
IMO that seems like a reasonable price to pay, if you want to see complete queries and bump the track_activity_query_size value up. regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
