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don-tay / simpledb

Subset of SQL-compliant DBMS
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Query using hash join implementation fails to run when stacked with many plans #31

Closed don-tay closed 2 years ago

don-tay commented 2 years ago

When a query uses a hash join, and has 3 or more plans (eg. group by, distinct, sort, joins/cross product)

Example query:

select distinct prof from student, enroll, section where sid=studentid and sectionid=sectid
Running hash join
Running index join
 prof
-----
java.lang.IndexOutOfBoundsException
        at java.base/java.nio.Buffer.checkIndex(Buffer.java:745)
        at java.base/java.nio.DirectByteBuffer.getInt(DirectByteBuffer.java:818)
        at simpledb.file.Page.getInt(Page.java:21)
        at simpledb.tx.Transaction.getInt(Transaction.java:117)
        at simpledb.record.RecordPage.getInt(RecordPage.java:32)
        at simpledb.record.TableScan.getInt(TableScan.java:48)
        at simpledb.record.TableScan.getVal(TableScan.java:57)
        at simpledb.materialize.HashJoinScan.next(HashJoinScan.java:80)
        at simpledb.query.SelectScan.next(SelectScan.java:34)
        at simpledb.index.query.IndexJoinScan.beforeFirst(IndexJoinScan.java:47)
        at simpledb.query.SelectScan.beforeFirst(SelectScan.java:30)
        at simpledb.query.ProjectScan.beforeFirst(ProjectScan.java:28)
        at simpledb.materialize.SortPlan.splitIntoRuns(SortPlan.java:95)
        at simpledb.materialize.SortPlan.open(SortPlan.java:42)
        at simpledb.plan.DistinctPlan.open(DistinctPlan.java:48)
        at test.SimpleIJ.doQuery(SimpleIJ.java:69)
        at test.SimpleIJ.main(SimpleIJ.java:39)

Similar results can be obtained for the query below, which has the same number of plans used by HeuristicQueryPlanner:

select prof from student,enroll,section where studentid=sid and sectionid=sectid group by prof