[HBASE-4570] Scan ACID problem with concurrent puts.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.90.1, 0.90.3
• Fix Version/s: 0.90.5
• Component/s: Client, regionserver
• Hadoop Flags: Reviewed
• Assignee: Jonathan Hsieh
• Reporter: Jonathan Hsieh
• Created: 10/Oct/11 23:05
• Updated: 20/Nov/15 11:55
• Resolved: 17/Oct/11 17:37

Description

When scanning a table sometimes rows that have multiple column families get split into two rows if there are concurrent writes. In this particular case we are overwriting the contents of a Get directly back onto itself as a Put.

For example, this is a two cf row (with "f1", "f2", .. "f9" cfs). It is actually returned as two rows (#55 and #56). Interestingly if the two were merged we would have a single proper row.

Row row0000024461 had time stamps: [55: keyvalues=

{row0000024461/f0:data/1318200440867/Put/vlen=1000, row0000024461/f0:qual/1318200440867/Put/vlen=10, row0000024461/f1:data/1318200440867/Put/vlen=1000, row0000024461/f1:qual/1318200440867/Put/vlen=10, row0000024461/f2:data/1318200440867/Put/vlen=1000, row0000024461/f2:qual/1318200440867/Put/vlen=10, row0000024461/f3:data/1318200440867/Put/vlen=1000, row0000024461/f3:qual/1318200440867/Put/vlen=10, row0000024461/f4:data/1318200440867/Put/vlen=1000, row0000024461/f4:qual/1318200440867/Put/vlen=10}

,
56: keyvalues=

{row0000024461/f5:data/1318200440867/Put/vlen=1000, row0000024461/f5:qual/1318200440867/Put/vlen=10, row0000024461/f6:data/1318200440867/Put/vlen=1000, row0000024461/f6:qual/1318200440867/Put/vlen=10, row0000024461/f7:data/1318200440867/Put/vlen=1000, row0000024461/f7:qual/1318200440867/Put/vlen=10, row0000024461/f8:data/1318200440867/Put/vlen=1000, row0000024461/f8:qual/1318200440867/Put/vlen=10, row0000024461/f9:data/1318200440867/Put/vlen=1000, row0000024461/f9:qual/1318200440867/Put/vlen=10}

]

I've only tested this on 0.90.1+patches and 0.90.3+patches, but it is consistent and duplicatable.

Issue Links

• relates to: HBASE-3498 Memstore scanner needs new semantics, which may require new data structure
• relates to: HBASE-4485 Eliminate window of missing Data
• relates to: HBASE-2670 MemStore should retain multiple KVs with the same timestamp when memstoreTS differs
• relates to: HBASE-2856 TestAcidGuarantee broken on trunk