terrymanu commented on issue #26537:
URL:
https://github.com/apache/shardingsphere/issues/26537#issuecomment-3639873908
## Understanding
- On 5.3.2 Proxy (PostgreSQL) with single tables enabled, SHOW SINGLE
TABLES LIKE 't_app_mon%' lists partition child tables on ds_8, but queries
without schema (parent or child) route to ds_0 and fail with “relation does not
exist.” Only queries with the actual schema
(e.g., xxx.t_app_mon_p202112) hit ds_8.
## Root Cause
- ShardingSphere-Proxy currently fixes the default schema to public and
does not support PostgreSQL search_path. Without an explicit schema, parsing
assumes public; if no single-table metadata matches, routing falls back to the
default single-table storage unit (shown
as RANDOM, effectively ds_0).
- 5.3.2 does not support PostgreSQL partition parent tables (relkind='p');
parent tables are not registered into single-table metadata, so even with
schema they fall back to the default route.
## Analysis
- SHOW SINGLE TABLES listing only child partitions (not the parent) shows
metadata is built from physical child tables.
- Logs sending schema-less SQL to ds_0 align with the default public
assumption and fallback behavior.
- Adding schema and querying the child partition routes to ds_8,
confirming single-table config works; the issues are default schema handling
plus unsupported partition parents.
## Conclusion
- Behavior matches current limitations rather than a confirmed defect.
Recommendations:
1. Always specify the schema in SQL; Proxy does not support
search_path, so use public as the default schema.
2. Avoid relying on PostgreSQL partition parent tables in Proxy; query
child partitions directly or use ShardingSphere sharding rules instead of
database partitions.
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