[HIVE-20552] Get Schema from LogicalPlan faster

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.2.0, 4.0.0-alpha-1
• Labels: pull-request-available
• Assignee: Teddy Choi
• Reporter: Teddy Choi
• Created: 13/Sep/18 07:24
• Updated: 27/Feb/24 22:23
• Resolved: 18/Dec/18 14:58

Description

To get the schema of a query faster, it currently needs to compile, optimize, and generate a TezPlan, which creates extra overhead when only the LogicalPlan is needed.

1. Copy the method HiveMaterializedViewsRegistry.parseQuery, making it public static and putting it in a utility class.
2. Change the return statement of the method to return analyzer.getResultSchema();
3. Change the return type of the method to List<FieldSchema>
4. Call the new method from GenericUDTFGetSplits.createPlanFragment replacing the current code which does this:

 if(num == 0) {
 //Schema only
 return new PlanFragment(null, schema, null);
 }

moving the call earlier in getPlanFragment ... right after the HiveConf is created ... bypassing the code that uses HiveTxnManager and Driver.
5. Convert the List<FieldSchema> to org.apache.hadoop.hive.llap.Schema.
6. return from getPlanFragment by returning {

{new PlanFragment(null, schema, null)}

}

Issue Links

• causes: HIVE-21041 NPE, ParseException in getting schema from logical plan
• links to: GitHub Pull Request #433
• links to: GitHub Pull Request #433