Hi, My first thought is pending list costs associated with the GIN indexes. https://pganalyze.com/blog/gin-index
You may be able to use pageinspect's function gin_metapage_info to see what the https://www.postgresql.org/docs/16/pageinspect.html#PAGEINSPECT-GIN-FUNCS https://gitlab.com/gitlab-com/gl-infra/production-engineering/-/issues/14386 Are you seeing HOT updates on the good example but not able to get HOT updates on the bad examples so all indexes need to get updated? You are updating checkOutByUID and CheckOutDateTime which don't appear to be indexes so HOT updates should be possible. Lowering the fill factor on the table may allow more HOT updates. If you change the fill factor you need to rebuild the table using pg_repack, etc. You could check for hot updates on the table with something like this. Select n_tup_upd, n_tup_hot_upd, round(100.0*n_tup_hot_upd / NULLIF(n_tup_upd,0), 1) as hot_pct from pg_stat_user_tables where relname = 'request'; https://www.crunchydata.com/blog/postgres-performance-boost-hot-updates-and-fill-factor https://pganalyze.com/blog/5mins-postgres-performance-HOT-updates-CLUSTER HTH. On Wed, 24 Sept 2025 at 05:41, Dirschel, Steve <steve.dirsc...@thomsonreuters.com> wrote: > > Postgres RDS running in AWS. PostgreSQL 16.8 on aarch64-unknown-linux-gnu, > compiled by gcc (GCC) 7.3.1 20180712 (Red Hat 7.3.1-17), 64-bit > > > > Table definition > > > > Table: request > > Column | Type | Collation | Nullable | > Default > > ------------------+-----------------------------+-----------+----------+---------------- > > objectid | character(36) | | not null | > > data | jsonb | | not null | > '{}'::jsonb > > clientid | character(3) | | not null | > > active | integer | | not null | > > productid | integer | | not null | > > checkoutbyuid | character(100) | | | > > checkoutdatetime | timestamp without time zone | | | > > metadata | jsonb | | not null | > '{}'::jsonb > > search_vector | tsvector | | | > > requeststate | text | | not null | > 'Active'::text > > Indexes: > > "requestkey" PRIMARY KEY, btree (objectid, productid) > > "idx_request_gin_data" gin (data) > > "idx_request_gin_data_i" gin ((data -> 'i'::text)) > > "idx_request_gin_data_r" gin ((data -> 'r'::text)) > > "idx_request_gin_data_t" gin ((data -> 't'::text)) > > "idx_request_gin_meta_identifiers" gin ((metadata -> 'identifiers'::text)) > > "idx_request_gin_metadata" gin (metadata) > > "idx_request_meta_identifiers" btree ((metadata ->> 'identifiers'::text)) > > Check constraints: > > "require_jsonb_data" CHECK (jsonb_typeof(data) = 'object'::text) > > "require_jsonb_metadata" CHECK (jsonb_typeof(metadata) = 'object'::text) > > Disabled user triggers: > > audit_trigger_row AFTER INSERT OR DELETE OR UPDATE ON request FOR EACH > ROW EXECUTE FUNCTION audit.audit_event_processor('true') > > audit_trigger_stm AFTER TRUNCATE ON request FOR EACH STATEMENT EXECUTE > FUNCTION audit.audit_event_processor('true' > > > > Lots of gin indexes... > > Note the 2 triggers are disabled. > > > > Size of the table, indexes, toast: > > > > table_name request > > row_estimate 227,771 > > total_bytes 12,952,428,544 > > index_bytes 6,088,523,776 > > toast_bytes 6,614,458,368 > > table_bytes 249,446,400 > > total 12 GB > > index 5806 MB > > toast 6308 MB > > table 238 MB > > > > > > We are updating some sample rows. Here are the sizes of the 2 JSONB columns > for these sample rows: > > > > select objectid, pg_column_size(data) data, pg_column_size(metadata) > metadata, clientid > > from request r > > order by pg_column_size(data) desc > > limit 4; > > > > objectid data metadata clientid > > f9077561-4b40-41f8-8a52-3a2b83014982 22172347 842 VHW > <---- update #1 below > > 0103fe5d-7407-45b6-8966-32a8e4f6b67c 17814078 866 OV9 > <---- update #2 below > > 6009dbfc-8375-48b3-bbf6-921d48aad308 15971425 879 VHW > > 3a0201bc-23f0-b648-8408-c21f81f6b974 14690119 785 VHU > <---- update #3 below > > > > > > *** Update the top row above which is the largest for the DATA JSONB column: > > > > explain(analyze, buffers) > > UPDATE request > > SET > > checkOutByUID = 'shivatest', > > CheckOutDateTime = '2022-01-10T16:24:10.2900556Z' > > WHERE > > objectid = 'f9077561-4b40-41f8-8a52-3a2b83014982'; > > > > Update on request (cost=0.42..8.44 rows=0 width=0) (actual > time=74.678..74.679 rows=0 loops=1) > > Buffers: shared hit=2818 read=1 dirtied=1 > > I/O Timings: shared read=0.835 > > -> Index Scan using requestkey on request (cost=0.42..8.44 rows=1 > width=418) (actual time=0.875..0.878 rows=1 loops=1) > > Index Cond: (objectid = > 'f9077561-4b40-41f8-8a52-3a2b83014982'::bpchar) > > Buffers: shared hit=3 read=1 > > I/O Timings: shared read=0.835 > > Planning Time: 0.093 ms > > Execution Time: 74.707 ms > > > > *** 2818 shared block hits, 1 read, 1 dirtied. Excellent. > > > > > > *** Update the next largest row > > > > explain(analyze, buffers) UPDATE request > > SET > > checkOutByUID = 'shivatest', > > CheckOutDateTime = '2022-01-10T16:24:10.2900556Z' > > WHERE > > objectid = '0103fe5d-7407-45b6-8966-32a8e4f6b67c'; > > > > Update on request (cost=0.42..8.44 rows=0 width=0) (actual > time=34663.039..34663.040 rows=0 loops=1) > > Buffers: shared hit=10787339 read=79854 dirtied=90531 > > I/O Timings: shared read=5083.198 > > -> Index Scan using requestkey on request (cost=0.42..8.44 rows=1 > width=418) (actual time=0.908..0.912 rows=1 loops=1) > > Index Cond: (objectid = > '0103fe5d-7407-45b6-8966-32a8e4f6b67c'::bpchar) > > Buffers: shared hit=3 read=1 > > I/O Timings: shared read=0.868 > > Planning Time: 0.095 ms > > Execution Time: 34663.071 ms > > > > Wow- 10 million shared block reads... 90k dirtied... update it again: > Same deal with shared blocks at 10M. Dirtied came down but shared blocks is > still extremely high. > > > > Update on request (cost=0.42..8.44 rows=0 width=0) (actual > time=27683.165..27683.166 rows=0 loops=1) > > Buffers: shared hit=10846051 read=145 dirtied=1189 > > I/O Timings: shared read=73.607 > > -> Index Scan using requestkey on request (cost=0.42..8.44 rows=1 > width=418) (actual time=0.021..0.033 rows=1 loops=1) > > Index Cond: (objectid = > '0103fe5d-7407-45b6-8966-32a8e4f6b67c'::bpchar) > > Buffers: shared hit=6 > > Planning Time: 0.095 ms > > Execution Time: 27683.197 ms > > > > > > *** Update the 4th largest row: > > > > explain(analyze, buffers) UPDATE request > > SET > > checkOutByUID = 'shivatest', > > CheckOutDateTime = '2022-01-10T16:24:10.2900556Z' > > WHERE > > objectid = '3a0201bc-23f0-b648-8408-c21f81f6b974'; > > > > > > Update on request (cost=0.42..8.44 rows=0 width=0) (actual > time=18179.058..18179.059 rows=0 loops=1) > > Buffers: shared hit=2138731 read=37045 dirtied=50800 > > I/O Timings: shared read=6030.123 > > -> Index Scan using requestkey on request (cost=0.42..8.44 rows=1 > width=418) (actual time=0.864..0.868 rows=1 loops=1) > > Index Cond: (objectid = > '3a0201bc-23f0-b648-8408-c21f81f6b974'::bpchar) > > Buffers: shared hit=3 read=1 > > I/O Timings: shared read=0.825 > > Planning Time: 0.085 ms > > Execution Time: 18179.090 ms > > > > And run it a second time: > > > > Update on request (cost=0.42..8.44 rows=0 width=0) (actual > time=10553.022..10553.023 rows=0 loops=1) > > Buffers: shared hit=2159422 dirtied=17 > > -> Index Scan using requestkey on request (cost=0.42..8.44 rows=1 > width=418) (actual time=0.022..0.032 rows=1 loops=1) > > Index Cond: (objectid = > '3a0201bc-23f0-b648-8408-c21f81f6b974'::bpchar) > > Buffers: shared hit=6 > > Planning Time: 0.093 ms > > Execution Time: 10553.056 ms > > > > 2.1 million shared block reads, the first update did 50k dirtied... > > > > At 2.1 million shared block reads with an 8k block size that is 16 GB of data > read in memory. At 10 million that is 76 GB of data read in memory. The > entire table, indexes, toast is only 12 GB so what is this reading through > when it does 2 or 10 million shared block hits? The amount of work for the > first update which did 2818 shared block reads is what I'd expect but I have > no clue how to determine what this is doing when it's going through millions > of blocks in memory. > > > > Any insight would be much appreciated. > > > > Regards > > Steve > > > > This e-mail is for the sole use of the intended recipient and contains > information that may be privileged and/or confidential. If you are not an > intended recipient, please notify the sender by return e-mail and delete this > e-mail and any attachments. Certain required legal entity disclosures can be > accessed on our website: > https://www.thomsonreuters.com/en/resources/disclosures.html
