The part about gc refers to old sstable files on disk. After a compaction, the old files on disk will be deleted when garbage collection happens.
On Wed, Dec 1, 2010 at 7:31 AM, Ying Tang <ivytang0...@gmail.com> wrote: > I'm confused , plz ingore the mail above. > Here is my confusion , > posterior to 0.6.6/0.7 , minor compaction and major compaction both > can clean out rows 'tagged' tombstones , and generate a new , without > tombstones , sstable . > And the tombstones remains in memory ,waiting to be removed by jvm gc . > Am i right? > > On Wed, Dec 1, 2010 at 9:10 PM, Ying Tang <ivytang0...@gmail.com> wrote: > >> 1. So posterior to 0.6.6/0.7 , minor compaction and major compaction >> both can clean out rows 'tagged' tombstones , this kind of clean out >> doesn't mead remove it from the disk permanently. >> The real remove is done by the jvm GC ? >> 2. The intence of compaction is merging multi sstables into one , clean >> out the tombstone , let the un-tombstones rows be into a new ordered >> sstable ? >> >> >> >> On Wed, Dec 1, 2010 at 7:30 PM, Sylvain Lebresne <sylv...@yakaz.com>wrote: >> >>> On Wed, Dec 1, 2010 at 12:11 PM, Ying Tang <ivytang0...@gmail.com> >>> wrote: >>> > And i have another question , what's the difference between minor >>> > compaction and major compaction? >>> >>> A major compaction is a compaction that compact *all* the SSTables of a >>> given >>> column family (compaction compacts one CF at a time). >>> >>> Before https://issues.apache.org/jira/browse/CASSANDRA-1074 >>> (introduced in 0.6.6 and >>> recent 0.7 betas/rcs), major compactions where the only ones that removed >>> the >>> tombstones (see http://wiki.apache.org/cassandra/DistributedDeletes) >>> and this is the >>> reason major compaction exists. Now, with #1074, minor compactions >>> should remove most >>> if not all tombstones, so major compaction are not or much less useful >>> (it may depend on your >>> workload though as minor can't always delete the tombstones). >>> >>> -- >>> Sylvain >>> >>> > >>> > On 12/1/10, Chen Xinli <chen.d...@gmail.com> wrote: >>> >> 2010/12/1 Ying Tang <ivytang0...@gmail.com> >>> >> >>> >>> Every time cassandra creates a new sstable , it will call the >>> >>> CompactionManager.submitMinorIfNeeded ? And if the number of >>> memtables is >>> >>> beyond MinimumCompactionThreshold , the minor compaction will be >>> called. >>> >>> And there is also a method named CompactionManager.submitMajor , and >>> the >>> >>> call relationship is : >>> >>> >>> >>> NodeCmd -- > NodeProbe -->StorageService.forceTableCompaction --> >>> >>> Table.forceCompaction -->CompactionManager.performMajor --> >>> >>> CompactionManager.submitMajor >>> >>> >>> >>> ColumnFamilyStore.forceMajorCompaction --> >>> CompactionManager.performMajor >>> >>> --> CompactionManager.submitMajor >>> >>> >>> >>> >>> >>> HintedHandOffManager >>> >>> --> CompactionManager.submitMajor >>> >>> >>> >>> So i have 3 questions: >>> >>> 1. Once a new sstable has been created , >>> >>> CompactionManager.submitMinorIfNeeded will be called , >>> minorCompaction >>> >>> maybe called . >>> >>> But when will the majorCompaction be called ? Just the NodeCmd ? >>> >>> >>> >> >>> >> Yes, majorCompaction must be called manually from NodeCmd >>> >> >>> >> >>> >>> 2. Which jobs will minorCompaction and majorCompaction do ? >>> >>> Will minorCompaction delete the data that have been marked as >>> deleted >>> >>> ? >>> >>> And how about the major compaction ? >>> >>> >>> >> >>> >> Compaction only mark sstables as deleted. Deletion will be done when >>> there >>> >> are full gc, or node restarted. >>> >> >>> >> >>> >>> 3. When gc be called ? Every time compaction been called? >>> >>> >>> >> >>> >> GC has nothing to do with compaction, you may mistake the two >>> conceptions >>> >> >>> >> >>> >>> >>> >>> >>> >>> >>> >>> -- >>> >>> Best regards, >>> >>> >>> >>> Ivy Tang >>> >>> >>> >>> >>> >>> >>> >>> >>> >> >>> >> >>> >> -- >>> >> Best Regards, >>> >> Chen Xinli >>> >> >>> > >>> > >>> > -- >>> > Best regards, >>> > >>> > Ivy Tang >>> > >>> >> >> >> >> -- >> Best regards, >> >> Ivy Tang >> >> >> >> > > > -- > Best regards, > > Ivy Tang > > > >
