Issue 1:
Bug Report

Which version of ShardingSphere did you use?

master

Which project did you use? ShardingSphere-JDBC or ShardingSphere-Proxy?

Proxy

Expected behavior

Actual behavior

sharding_db=> alter table t_order
add constraint t_order_pk
primary key (order_id);
ERROR: duplicate key value violates unique constraint "pg_class_relname_nsp_index"
DETAIL: Key (relname, relnamespace)=(t_order_pk, 2200) already exists.

[INFO ] 2021-05-28 17:06:57.650 [pool-4-thread-1] ShardingSphere-SQL - Logic SQL: alter table t_order
add constraint t_order_pk
primary key (order_id);
[INFO ] 2021-05-28 17:06:57.650 [pool-4-thread-1] ShardingSphere-SQL - SQLStatement: PostgreSQLAlterTableStatement()
[INFO ] 2021-05-28 17:06:57.650 [pool-4-thread-1] ShardingSphere-SQL - Actual SQL: ds_1 ::: alter table t_order_0
add constraint t_order_pk
primary key (order_id);
[INFO ] 2021-05-28 17:06:57.650 [pool-4-thread-1] ShardingSphere-SQL - Actual SQL: ds_1 ::: alter table t_order_1
add constraint t_order_pk
primary key (order_id);
[INFO ] 2021-05-28 17:06:57.650 [pool-4-thread-1] ShardingSphere-SQL - Actual SQL: ds_0 ::: alter table t_order_0
add constraint t_order_pk
primary key (order_id);
[INFO ] 2021-05-28 17:06:57.650 [pool-4-thread-1] ShardingSphere-SQL - Actual SQL: ds_0 ::: alter table t_order_1
add constraint t_order_pk
primary key (order_id);
[ERROR] 2021-05-28 17:06:57.656 [pool-4-thread-1] o.a.s.p.f.c.CommandExecutorTask - Exception occur:
org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "pg_class_relname_nsp_index"
Detail: Key (relname, relnamespace)=(t_order_pk, 2200) already exists.
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2440)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2183)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:308)
at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365)
at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:307)
at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:293)
at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:270)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:266)
at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:1168)
at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:106)
at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java)
at org.apache.shardingsphere.proxy.backend.communication.jdbc.executor.callback.impl.ProxyStatementExecutorCallback.execute(ProxyStatementExecutorCallback.java:40)
at org.apache.shardingsphere.proxy.backend.communication.jdbc.executor.callback.ProxyJDBCExecutorCallback.executeSQL(ProxyJDBCExecutorCallback.java:73)
at org.apache.shardingsphere.proxy.backend.communication.jdbc.executor.callback.ProxyJDBCExecutorCallback.executeSQL(ProxyJDBCExecutorCallback.java:66)
at org.apache.shardingsphere.proxy.backend.communication.jdbc.executor.callback.ProxyJDBCExecutorCallback.executeSQL(ProxyJDBCExecutorCallback.java:44)
at org.apache.shardingsphere.infra.executor.sql.execute.engine.driver.jdbc.JDBCExecutorCallback.execute(JDBCExecutorCallback.java:85)
at org.apache.shardingsphere.infra.executor.sql.execute.engine.driver.jdbc.JDBCExecutorCallback.execute(JDBCExecutorCallback.java:64)
at org.apache.shardingsphere.infra.executor.kernel.ExecutorEngine.syncExecute(ExecutorEngine.java:101)
at org.apache.shardingsphere.infra.executor.kernel.ExecutorEngine.parallelExecute(ExecutorEngine.java:97)
at org.apache.shardingsphere.infra.executor.kernel.ExecutorEngine.execute(ExecutorEngine.java:82)
at org.apache.shardingsphere.infra.executor.sql.execute.engine.driver.jdbc.JDBCExecutor.execute(JDBCExecutor.java:65)
at org.apache.shardingsphere.proxy.backend.communication.jdbc.executor.ProxyJDBCExecutor.execute(ProxyJDBCExecutor.java:64)
at org.apache.shardingsphere.proxy.backend.communication.ProxySQLExecutor.useDriverToExecute(ProxySQLExecutor.java:165)
at org.apache.shardingsphere.proxy.backend.communication.ProxySQLExecutor.execute(ProxySQLExecutor.java:124)
at org.apache.shardingsphere.proxy.backend.communication.ProxySQLExecutor.execute(ProxySQLExecutor.java:113)
at org.apache.shardingsphere.proxy.backend.communication.ProxyLockEngine.doExecute(ProxyLockEngine.java:103)
at org.apache.shardingsphere.proxy.backend.communication.ProxyLockEngine.execute(ProxyLockEngine.java:81)
at org.apache.shardingsphere.proxy.backend.communication.DatabaseCommunicationEngine.execute(DatabaseCommunicationEngine.java:98)
at org.apache.shardingsphere.proxy.backend.text.data.impl.SchemaAssignedDatabaseBackendHandler.execute(SchemaAssignedDatabaseBackendHandler.java:55)
at org.apache.shardingsphere.proxy.frontend.postgresql.command.query.text.PostgreSQLComQueryExecutor.execute(PostgreSQLComQueryExecutor.java:65)
at org.apache.shardingsphere.proxy.frontend.command.CommandExecutorTask.executeCommand(CommandExecutorTask.java:93)
at org.apache.shardingsphere.proxy.frontend.command.CommandExecutorTask.run(CommandExecutorTask.java:71)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

Reason analyze (If you can)

Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.

Example codes for reproduce this issue (such as a github link).

Issue 2:
Question

Where can I find the use example of "Like query column" in the project？？