[KYLIN-5016] Avoid potential NPE issue in RDBMS Pushdown case

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: v2.6.5, v3.1.2
• Fix Version/s: v3.1.3
• Component/s: RDBMS Source
• Assignee: rongchuan.jin
• Reporter: rongchuan.jin
• Created: 25/Jun/21 02:32
• Updated: 06/Jan/22 06:54
• Resolved: 27/Jun/21 08:05

Description

When I use pushdown with RDBMS source, I encounter some error when convert sql which leads to pushdown failing.

I find below stacktrace like

2020-12-23 13:14:10,212 ERROR [Query a1bf28bb-de28-433e-ab96-28ce234a1a4a-76] conv.SqlConverter : Failed to default convert sql, will use the origin input: select 1 from `MOVIES_10M`.`DIM_MOVIES_10M` 2LIMIT 500 3java.lang.NullPointerException 4 at org.apache.calcite.sql.SqlCall.unparse(SqlCall.java:103) 5 at org.apache.calcite.sql.pretty.SqlPrettyWriter.format(SqlPrettyWriter.java:806) 6 at org.apache.kylin.sdk.datasource.framework.conv.SqlConverter.convertSql(SqlConverter.java:69) 7 at org.apache.kylin.sdk.datasource.framework.JdbcConnector.convertSql(JdbcConnector.java:91) 8 at org.apache.kylin.sdk.datasource.PushDownRunnerSDKImpl.executeQuery(PushDownRunnerSDKImpl.java:55) 9 at org.apache.kylin.query.util.PushDownUtil.tryPushDownQuery(PushDownUtil.java:173) 10 at org.apache.kylin.query.util.PushDownUtil.tryPushDownSelectQuery(PushDownUtil.java:103) 11 at org.apache.kylin.rest.service.QueryService.tryPushDownSelectQuery(QueryService.java:773) 12 at org.apache.kylin.rest.service.QueryService.pushDownQuery(QueryService.java:709) 13 at org.apache.kylin.rest.service.QueryService.queryWithSqlMassage(QueryService.java:700) 14 at org.apache.kylin.rest.service.QueryService.query(QueryService.java:231) 15 at org.apache.kylin.rest.service.QueryService.queryAndUpdateCache(QueryService.java:577) 16 at org.apache.kylin.rest.service.QueryService.queryWithCache(QueryService.java:512) 17 at org.apache.kylin.rest.service.QueryService.doQueryWithCache(QueryService.java:395)