Omnisharded tables routing fix

[levkk]

Description

• Omnisharded tables detection in SELECT handler wasn't parsing table names correctly from the FROM clause, i.e. didn't support joins.
• Fix expanded explain with omni tables.

pgdog=# explain SELECT n.nspname as "Schema",
pgdog-#   c.relname as "Name",
pgdog-#   CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'm' THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 't' THEN 'TOAST table' WHEN 'f' THEN 'foreign table' WHEN 'p' THEN 'partitioned table' WHEN 'I' THEN 'partitioned index' END as "Type",
pgdog-#   pg_catalog.pg_get_userbyid(c.relowner) as "Owner",
pgdog-#   CASE c.relpersistence WHEN 'p' THEN 'permanent' WHEN 't' THEN 'temporary' WHEN 'u' THEN 'unlogged' END as "Persistence",
pgdog-#   am.amname as "Access method",
pgdog-#   pg_catalog.pg_size_pretty(pg_catalog.pg_table_size(c.oid)) as "Size",
pgdog-#   pg_catalog.obj_description(c.oid, 'pg_class') as "Description"
pgdog-# FROM pg_catalog.pg_class c
pgdog-#      LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
pgdog-#      LEFT JOIN pg_catalog.pg_am am ON am.oid = c.relam
pgdog-# WHERE c.relkind IN ('r','p','v','m','S','f','')
pgdog-#       AND n.nspname <> 'pg_catalog'
pgdog-#       AND n.nspname !~ '^pg_toast'
pgdog-#       AND n.nspname <> 'information_schema'
pgdog-#   AND pg_catalog.pg_table_is_visible(c.oid)
pgdog-# ORDER BY 1,2;
                                                                        QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------------------------------
 Result  (cost=36.89..47.39 rows=35 width=384)
   ->  Sort  (cost=36.89..36.98 rows=35 width=324)
         Sort Key: n.nspname, c.relname
         ->  Hash Left Join  (cost=2.25..35.99 rows=35 width=324)
               Hash Cond: (c.relam = am.oid)
               ->  Hash Join  (cost=1.09..33.55 rows=35 width=142)
                     Hash Cond: (c.relnamespace = n.oid)
                     ->  Seq Scan on pg_class c  (cost=0.00..32.07 rows=70 width=82)
                           Filter: ((relkind = ANY ('{r,p,v,m,S,f,""}'::"char"[])) AND pg_table_is_visible(oid))
                     ->  Hash  (cost=1.07..1.07 rows=2 width=68)
                           ->  Seq Scan on pg_namespace n  (cost=0.00..1.07 rows=2 width=68)
                                 Filter: ((nspname <> 'pg_catalog'::name) AND (nspname !~ '^pg_toast'::text) AND (nspname <> 'information_schema'::name))
               ->  Hash  (cost=1.07..1.07 rows=7 width=68)
                     ->  Seq Scan on pg_am am  (cost=0.00..1.07 rows=7 width=68)

 PgDog Routing:
   Summary: shard=1 role=replica
   Shard 1: SELECT matched omnisharded tables: pg_class, pg_namespace, pg_am
(18 rows)

[codecov]

Codecov Report

❌ Patch coverage is 84.28571% with 11 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/frontend/router/parser/query/select.rs	60.86%	9 Missing ⚠️
pgdog/src/frontend/router/parser/from_clause.rs	95.65%	1 Missing ⚠️
pgdog/src/frontend/router/parser/where_clause.rs	80.00%	1 Missing ⚠️

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