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Posted to notifications@shardingsphere.apache.org by "Imdyh (via GitHub)" <gi...@apache.org> on 2026/04/17 10:01:59 UTC
[I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Imdyh opened a new issue, #38635:
URL: https://github.com/apache/shardingsphere/issues/38635
I cannot obtain shard table information from Information_SCHEMA.LUMNS, but I can obtain it from the actual shard table
<img width="1126" height="390" alt="Image" src="https://github.com/user-attachments/assets/433cd339-501c-4b51-8268-efa1902fe5df" />
<img width="967" height="371" alt="Image" src="https://github.com/user-attachments/assets/9c93e811-8a75-446f-9914-eca424429881" />
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on issue #38635:
URL: https://github.com/apache/shardingsphere/issues/38635#issuecomment-4348209077
There hasn't been any activity on this issue recently, and in order to prioritize active issues, it will be marked as stale.
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "terrymanu (via GitHub)" <gi...@apache.org>.
terrymanu commented on issue #38635:
URL: https://github.com/apache/shardingsphere/issues/38635#issuecomment-4272713387
Problem Understanding
Fast triage:
Reproduction package complete: No. Issue [#38635](https://github.com/apache/shardingsphere/issues/38635) has screenshots, but no ShardingSphere version, topology, DB version, rule config, or logs.
Expected behavior explicitly documented: No. I did not find official docs promising that information_schema.columns must expose logical sharding tables. The official docs instead say Proxy has limited support for system tables like information_schema: [Quick Start](https://shardingsphere.apache.org/document/current/en/quick-start/shardingsphere-proxy-quick-start/).
Code/tests contradict that doc boundary: No clear contradiction found.
Provisional type: Needs More Info, leaning Misunderstanding / Invalid Usage rather than confirmed Bug.
Root Cause
OBS-1: The issue screenshot shows SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'zyhl_ims' AND TABLE_NAME in('test_sharding') returns no rows, while the same query for physical tables test_sharding_0 and test_sharding_1 returns column rows. Source: [issue #38635](https://github.com/apache/shardingsphere/issues/38635).
OBS-2: Official docs state that Proxy provides limited support for system databases / tables such as information_schema. Source: [Quick Start](https://shardingsphere.apache.org/document/current/en/quick-start/shardingsphere-proxy-quick-start/).
OBS-3: Official docs provide logical metadata queries through DistSQL, including [SHOW TABLE METADATA](https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/syntax/ral/show-table-metadata/) and [SHOW SHARDING TABLE NODES](https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/syntax/rql/rule-query/sharding/show-sharding-table-nodes/).
OBS-4: The MySQL Proxy system-schema factory only registers a special executor for SCHEMATA; other system tables fall back to a generic metadata executor. Source: MySQLSystemSchemaQueryExecutorFactory.java (line 41), MySQLSchemataQueryExecutorFactory.java (line 29).
OBS-5: The generic executor opens a backend storage-unit connection and executes the original SQL directly; it does not rewrite logical table names for information_schema.columns. Source: DatabaseMetaDataExecutor.java (line 95).
OBS-6: Tests cover the SCHEMATA special case and generic fallback, but I did not find a MySQL Proxy test asserting logical-table exposure via information_schema.columns. Source: MySQLAdminExecutorCreatorTest.java (line 326), MySQLSystemSchemaQueryExecutorFactoryTest.java (line 89), SelectInformationSchemataExecutorTest.java (line 109).
INF-1: From OBS-1, OBS-4, and OBS-5, the empty result for logical table test_sharding is consistent with current Proxy behavior: information_schema.columns is answered from backend MySQL metadata, which knows physical tables but not ShardingSphere logical table names. Confidence: Medium.
INF-2: From OBS-2, OBS-3, OBS-4, and OBS-5, the current behavior appears aligned with documented limited information_schema support, while documented logical metadata access is through DistSQL instead. Confidence: Medium.
INF-3: Because version, mode, DB version, and config are missing, I cannot rule out a version-specific regression or an environment-specific metadata bug. Confidence: Low.
Problem Analysis
The repo already exposes logical-table metadata through native Proxy paths:
SHOW TABLES reads ShardingSphere schema metadata, not just backend physical tables. Source: MySQLShowTablesExecutor.java (line 80).
SHOW TABLE METADATA is the documented table-metadata query API for logical tables. Source: [docs](https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/syntax/ral/show-table-metadata/).
SHOW SHARDING TABLE NODES is the documented logical-to-physical mapping query. Source: [docs](https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/syntax/rql/rule-query/sharding/show-sharding-table-nodes/).
So the current evidence shows a gap between a client-style information_schema.columns expectation and the currently documented/supported logical metadata APIs, not a verified doc/code mismatch.
Missing evidence that blocks a definitive conclusion:
ShardingSphere version
Proxy vs JDBC confirmation
Standalone vs Cluster
MySQL version
Minimal sharding rule/config for test_sharding
Exact outputs of SHOW TABLES, SHOW TABLE METADATA test_sharding, and SHOW SHARDING TABLE NODES test_sharding
Whether this was run from mysql CLI or a GUI client
Relevant proxy log lines, if any
Problem Conclusion
Current classification: Needs More Info, with a provisional leaning toward Misunderstanding / Invalid Usage.
Reason: the report is missing the minimum reproduction package, and the verified docs/code point to limited information_schema support plus backend-pass-through behavior for information_schema.columns. This conclusion is supported by OBS-1, OBS-2, OBS-4, OBS-5, INF-1, and INF-2.
Minimum follow-up request to the reporter:
ShardingSphere version
Access mode and governance mode
MySQL version
Sharding rule snippet for test_sharding
Exact outputs of the four SQL statements listed above
Client type: mysql CLI or GUI tool
Follow-up window: 7-14 days. If no extra evidence arrives, closing as status: invalid would be reasonable.
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "Imdyh (via GitHub)" <gi...@apache.org>.
Imdyh commented on issue #38635:
URL: https://github.com/apache/shardingsphere/issues/38635#issuecomment-4274007898
ShardingSphere version is 5.5.2，use Standalone mode，mysql version is 8.0.30，tried via mysql CLI and GUI client，no logs were printed, including those for success and exceptions
Configuration as follows：
[database-sharding.yaml](https://github.com/user-attachments/files/26856757/database-sharding.yaml)
Exact output as follows:
<img width="489" height="253" alt="Image" src="https://github.com/user-attachments/assets/aeac3f29-ba64-46ac-899f-a273c0e64aec" />
<img width="1277" height="315" alt="Image" src="https://github.com/user-attachments/assets/da152903-e3f6-4e04-871d-7ef552b6813b" />
<img width="1323" height="241" alt="Image" src="https://github.com/user-attachments/assets/11c4f8ad-9423-40b4-afd0-ae1d3f6a1cba" />
<img width="1029" height="265" alt="Image" src="https://github.com/user-attachments/assets/6b22c623-9bc3-4969-8863-b5f1b52c5c21" />
<img width="1387" height="523" alt="Image" src="https://github.com/user-attachments/assets/4a170046-66b9-4f1b-93d8-bdd1bce495a0" />
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "Imdyh (via GitHub)" <gi...@apache.org>.
Imdyh commented on issue #38635:
URL: https://github.com/apache/shardingsphere/issues/38635#issuecomment-4294658160
@terrymanu Please review it again
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on issue #38635:
URL: https://github.com/apache/shardingsphere/issues/38635#issuecomment-4597327593
There hasn't been any activity on this issue recently, and in order to prioritize active issues, it will be marked as stale.
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "terrymanu (via GitHub)" <gi...@apache.org>.
terrymanu commented on issue #38635:
URL: https://github.com/apache/shardingsphere/issues/38635#issuecomment-4531808148
Conclusion: this is not a confirmed bug. It is best classified as Misunderstanding / Invalid Usage: information_schema.columns does not currently promise logical sharding-table metadata in Proxy.
1. Problem Understanding
Fast triage:
Reproducible evidence: mostly yes. The reporter provided ShardingSphere 5.5.2, Standalone mode, MySQL 8.0.30, Proxy YAML, SQL screenshots, and “no logs”.
Documented expectation: no. 5.5.2 docs state Proxy has limited support for system databases/tables such as information_schema ([docs](https://shardingsphere.apache.org/document/5.5.2/en/quick-start/shardingsphere-proxy-quick-start/)).
Code/test mismatch: no clear mismatch found.
Topology:
Access mode: Proxy, inferred from database-sharding.yaml and Proxy DistSQL screenshots.
Governance mode: Standalone.
Registry/config center: N/A.
Database: MySQL 8.0.30.
2. Root Cause
Observations:
OBS-1: Issue #38635 reports information_schema.columns returns rows for physical tables like test_sharding_0, but not logical table test_sharding ([issue](https://github.com/apache/shardingsphere/issues/38635)).
OBS-2: The attached YAML defines logical table test_sharding with actual nodes ds_0.test_sharding_${0..9} and an INLINE sharding algorithm. Source: issue attachment database-sharding.yaml.
OBS-3: Screenshots show SHOW TABLES, SHOW TABLE METADATA test_sharding, and SHOW SHARDING TABLE NODES test_sharding return logical metadata/nodes. Source: issue comment screenshots.
OBS-4: 5.5.2 docs define SHOW TABLE METADATA as the metadata query syntax ([docs](https://shardingsphere.apache.org/document/5.5.2/en/user-manual/shardingsphere-proxy/distsql/syntax/ral/show-table-metadata/)).
OBS-5: 5.5.2 docs define SHOW SHARDING TABLE NODES for sharding node queries ([docs](https://shardingsphere.apache.org/document/5.5.2/en/user-manual/shardingsphere-proxy/distsql/syntax/rql/rule-query/sharding/show-sharding-table-nodes/)).
OBS-6: In tag 5.5.2, MySQLInformationSchemaExecutorFactory special-cases only SCHEMATA; other information_schema system tables use DefaultDatabaseMetaDataExecutor. Path: proxy/backend/type/mysql/src/main/java/.../MySQLInformationSchemaExecutorFactory.java.
OBS-7: DefaultDatabaseMetaDataExecutor directly prepares and executes the original SQL on one backend storage-unit connection. Path: proxy/backend/core/src/main/java/.../AbstractDatabaseMetaDataExecutor.java.
OBS-8: 5.5.2 tests confirm default metadata executor behavior for non-SCHEMATA information-schema tables. Path: proxy/backend/type/mysql/src/test/java/.../MySQLAdminExecutorCreatorTest.java.
Inferences:
INF-1 from OBS-1, OBS-6, OBS-7: information_schema.columns is querying backend MySQL physical metadata, so it can see test_sharding_0...9 but not logical test_sharding. Confidence: High.
INF-2 from OBS-3, OBS-4, OBS-5: ShardingSphere already exposes the requested logical metadata through DistSQL, not through information_schema.columns. Confidence: High.
INF-3 from OBS-2, OBS-6, OBS-7: The YAML sharding rule is not the root cause; the behavior follows the Proxy system-schema query path. Confidence: Medium.
3. Problem Analysis
The reporter’s expectation is understandable, but it is outside the documented guarantee. ShardingSphere defines logical vs actual tables in the sharding concept [docs](https://shardingsphere.apache.org/document/5.5.2/en/features/sharding/concept/) (docs), and Proxy docs explicitly limit system-table support.
Current 5.5.2 behavior is internally consistent:
SHOW TABLES and DistSQL read ShardingSphere metadata.
information_schema.columns falls through to backend MySQL metadata for non-special system tables.
Backend MySQL knows physical tables, not ShardingSphere logical table names.
So the root cause is not a sharding-rule failure. It is an unsupported expectation that MySQL information_schema.columns should be logically projected by Proxy.
4. Problem Conclusion
Classification: Misunderstanding / Invalid Usage, not Bug.
This conclusion is supported by OBS-1, OBS-3, OBS-4, OBS-5, OBS-6, OBS-7, INF-1, and INF-2.
Recommended issue response:
Explain that information_schema.columns logical table projection is not supported in 5.5.2.
Point to SHOW TABLE METADATA test_sharding and SHOW SHARDING TABLE NODES test_sharding as the documented metadata paths.
Close as status: invalid, unless maintainers want to convert it into a separate enhancement for MySQL-compatible logical information_schema.columns projection.
Evidence Confidence: Medium
Impact Scope: Proxy metadata query behavior, MySQL information_schema.columns, sharding logical-table metadata
Topology: Proxy + Standalone
Issue Type: Misunderstanding / Invalid Usage
Recommended Labels: type: question, status: invalid, optionally in: Proxy, db: MySQL
Next Action: close as unsupported usage, or reopen as enhancement only if maintainers want new Proxy compatibility behavior.
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Re: [I] can not obtain Information_SCHEMA.LUMNS [shardingsphere]
Posted by "terrymanu (via GitHub)" <gi...@apache.org>.
terrymanu closed issue #38635: can not obtain Information_SCHEMA.LUMNS
URL: https://github.com/apache/shardingsphere/issues/38635
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