sql: Add contended tables, indexes, and keys views

[awoods187]

We now have rich contention information on contention, but we require developers to find it and address it themselves. Instead, we could make predetermined views that would ease observability.

Contended tables:

CREATE VIEW crdb_internal.contended_tables (database_name, schema_name, name, num_contention_events)
AS SELECT DISTINCT database_name, schema_name, name, num_contention_events
FROM crdb_internal.cluster_contention_events
JOIN crdb_internal.tables
ON crdb_internal.cluster_contention_events.table_id = crdb_internal.tables.table_id
ORDER BY num_contention_events desc;

With sample TPC-C results:

select * from contended_tables;
  database_name | schema_name |       name       | num_contention_events
----------------+-------------+------------------+------------------------
  tpcc          | public      | warehouse        |                   496
  system        | public      | jobs             |                   178
  tpcc          | public      | district         |                    71
  system        | public      | sqlliveness      |                    51
  NULL          | pg_catalog  | pg_extension     |                    33
  system        | public      | jobs             |                    33
  tpcc          | public      | stock            |                     9
  NULL          | pg_catalog  | pg_event_trigger |                     9
  NULL          | pg_catalog  | pg_event_trigger |                     6
  NULL          | pg_catalog  | pg_event_trigger |                     4
  NULL          | pg_catalog  | pg_event_trigger |                     3
  NULL          | pg_catalog  | pg_event_trigger |                     2
  NULL          | pg_catalog  | pg_event_trigger |                     1

We should also add views for contended indexes and contended keys.

CREATE VIEW tpcc.contended_indexes (database_name, schema_name, name, index_name, num_contention_events)
AS SELECT DISTINCT database_name, schema_name, name, index_name, num_contention_events
FROM crdb_internal.cluster_contention_events, crdb_internal.tables, crdb_internal.table_indexes
WHERE crdb_internal.cluster_contention_events.index_id = crdb_internal.table_indexes.index_id
AND crdb_internal.cluster_contention_events.table_id = crdb_internal.tables.table_id
ORDER BY num_contention_events desc limit 5;
 SELECT * from contended_indexes;
  database_name | schema_name |    name     | index_name | num_contention_events
----------------+-------------+-------------+------------+------------------------
  tpcc          | public      | warehouse   | primary    |                   812
  system        | public      | jobs        | primary    |                   182
  tpcc          | public      | district    | primary    |                   142
  system        | public      | sqlliveness | primary    |                    55
  system        | public      | jobs        | order_idx  |                    34
(5 rows)