Add Inspect Progress Of Long-Running Create Index as a Postgres til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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-_1192 TILs and counting..._
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@@ -606,6 +606,7 @@ _1192 TILs and counting..._
 - [Include All Queries In The Log File](postgres/include-all-queries-in-the-log-file.md)
 - [Insert A Bunch Of Records With Generate Series](postgres/insert-a-bunch-of-records-with-generate-series.md)
 - [Insert Just The Defaults](postgres/insert-just-the-defaults.md)
+- [Inspect Progress Of Long-Running Create Index](postgres/inspect-progress-of-long-running-create-index.md)
 - [Install Postgres With uuid-ossp Using asdf](postgres/install-postgres-with-uuid-ossp-using-asdf.md)
 - [Integers In Postgres](postgres/integers-in-postgres.md)
 - [Intervals Of Time By Week](postgres/intervals-of-time-by-week.md)

postgres/inspect-progress-of-long-running-create-index.md

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+# Inspect Progress Of Long-Running Create Index
+
+Strategically applied indexes are an important part of keeping queries against
+a database fast. Initially applying those indexes—especially for large tables
+in production—can take a bit of time.
+
+The `create index` call doesn't provide any indication of progress. So if
+applying an index takes minutes or even hours, it can be disconcerting.
+
+Is it still working or is it locked up? How far along is it?
+
+Postgres tracks the index creation process in `pg_stat_progress_create_index`
+and we can query that table.
+
+```sql
+select
+  now()::time(0), 
+  a.query, 
+  p.phase, 
+  p.blocks_total, 
+  p.blocks_done, 
+  p.tuples_total, 
+  p.tuples_done,
+  ai.schemaname,
+  ai.relname,
+  ai.indexrelname
+from pg_stat_progress_create_index p 
+join pg_stat_activity a on p.pid = a.pid
+left join pg_stat_all_indexes ai on ai.relid = p.relid and ai.indexrelid = p.index_relid;
+```
+
+There are a bunch of phases that Postgres goes through to create the index,
+especially if it is being created `concurrently`. The `blocks_done` and
+`tuples_done` numbers will keep ticking along, giving you an indication that
+the process is proceeding.
+
+[source one](https://dba.stackexchange.com/a/249784) and [source two](https://www.depesz.com/2019/04/18/waiting-for-postgresql-12-report-progress-of-create-index-operations/)