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.
It is not only about analytical workloads. I see it for regular OLTP
workloads literally *any* large project that use an ORM. Ruby on Rails'
ActiveRecord does it, Java'sHibernate does, and so on.
As a result, many queries exceed track_activity_query_size, and we
end up having queries trimmed in pg_stat_activity. Why it is bad:- it
makes an automated analysis involving pg_stat_activity impossible,
it complicates any manual troubleshooting involving pg_stat_activity.
Changing this parameter in a mission-critical database is difficult
because it requires a restart.
+1 for changing it to 1M or at least to 100k. If the penalty is significant,
at least 10k.
What is the overhead here except the memory consumption?
Consumption of, say,100 * 1M = 1MiB of RAM is a low price for much
better transparency here. But what about the performance penalty?
Some benchmark would be nice to answer this.
On Fri, Dec 20, 2019 at 08:57:04AM -0500, Bruce Momjian wrote:
> I can imagine using larger pgstat_track_activity_query_size values for
> data warehouse queries, where they are long and there are only a few of
> them.
Why are those queries that long anyway? A too long IN clause with an
insane amount of parameters which could be replaced by an ANY clause
with an array?
--
Michael
