[PHOENIX-7238] Queries that use an uncovered index with SALT_BUCKETS=0, we get /0 error

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Hari Krishna Dara
• Created: 26/Feb/24 14:46
• Updated: 27/Feb/24 01:38

Description

I have not done extensive testing on it, but when I specified SALT_BUCKETS=0 while creating an index, I get no error and this is a valid use case to disable salting on index when the data table is salted:

create table tsalt (k INTEGER PRIMARY KEY, v1 INTEGER) SALT_BUCKETS=4;
upsert into tsalt (k, v1) VALUES (1, 100);
create uncovered index tsaltidx on tsalt (PHOENIX_ROW_TIMESTAMP()) SALT_BUCKETS=0;

 

From schema and hbase regions, it is correctly treated as no salting scenario.

 

0: jdbc:phoenix:localhost> select salt_buckets from system.catalog where table_name = 'TSALTIDX' and salt_buckets is not null;

--------------

SALT_BUCKETS

--------------
--------------
No rows selected (0.026 seconds)

 

hbase:001:0> list_regions 'TSALTIDX'
                   SERVER_NAME |                                               REGION_NAME |  START_KEY |    END_KEY |  SIZE |   REQ |   LOCALITY |
 ----------------------------- | --------------------------------------------------------- | ---------- | ---------- | ----- | ----- | ---------- |
 localhost,16020,1708958003582 | TSALTIDX,,1708958225506.a72b20c15cecba23289a03cd6956ec15. |            |            |     0 |     3 |        0.0 |
 1 rows

However, when I query through the index, I get an ArithmeticError for divide by zero.

{{0: jdbc:phoenix:localhost> select /*+ INDEX(TSALT TSALTIDX) */ * from TSALT;Caused by: java.lang.ArithmeticException: / by zero
        at org.apache.phoenix.schema.SaltingUtil.getSaltingByte(SaltingUtil.java:79)
        at org.apache.phoenix.index.IndexMaintainer.buildDataRowKey(IndexMaintainer.java:916)
        at org.apache.phoenix.coprocessor.UncoveredIndexRegionScanner.scanIndexTableRows(UncoveredIndexRegionScanner.java:253)
        at org.apache.phoenix.coprocessor.UncoveredIndexRegionScanner.scanIndexTableRows(UncoveredIndexRegionScanner.java:274)
        at org.apache.phoenix.coprocessor.UncoveredIndexRegionScanner.next(UncoveredIndexRegionScanner.java:382)
        at org.apache.phoenix.coprocessor.BaseRegionScanner.nextRaw(BaseRegionScanner.java:56)
        at org.apache.phoenix.iterate.RegionScannerFactory$1.nextRaw(RegionScannerFactory.java:257)

My suspicion is that table cells have number buckets stored as zero, so PTableImpl for the index gets constructed to return 0 from getBucketNum() and this is causing the divide by 0 error.

Issue Links

• blocks: PHOENIX-7001 Change Data Capture leveraging Max Lookback and Uncovered Indexes