3.2. Upgrading from 0.92.x to 0.94.x

0.92 and 0.94 are interface compatible. You can do a rolling upgrade between these versions. + 3.3. Upgrading from 0.92.x to 0.94.x

3.3. Upgrading from 0.92.x to 0.94.x
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3.3. Upgrading from 0.92.x to 0.94.x

0.92 and 0.94 are interface compatible. You can do a rolling upgrade between these versions.

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\ No newline at end of file Modified: hbase/hbase.apache.org/trunk/book/upgrading.html URL: http://svn.apache.org/viewvc/hbase/hbase.apache.org/trunk/book/upgrading.html?rev=1463652&r1=1463651&r2=1463652&view=diff ============================================================================== --- hbase/hbase.apache.org/trunk/book/upgrading.html (original) +++ hbase/hbase.apache.org/trunk/book/upgrading.html Tue Apr 2 18:06:19 2013 @@ -1,28 +1,39 @@ - Chapter 3. Upgrading

Chapter 3. Upgrading
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Chapter 3. Upgrading

Table of Contents

3.1. Upgrading from 0.94.x to 0.96.x

3.2. Upgrading from 0.92.x to 0.94.x

3.3. Upgrading from 0.90.x to 0.92.x

3.3.1. You can’t go back! -
3.3.2. MSLAB is ON by default -
3.3.3. Distributed splitting is on by default -
3.3.4. Memory accounting is different now -
3.3.5. On the Hadoop version to use -
3.3.6. HBase 0.92.0 ships with ZooKeeper 3.4.2 -
3.3.7. Online alter is off by default -
3.3.8. WebUI -
3.3.9. Security tarball -
3.3.10. Experimental off-heap cache -
3.3.11. Changes in HBase replication -
3.3.12. RegionServer now aborts if OOME -
3.3.13. HFile V2 and the “Bigger, Fewer” Tendency -

3.4. Upgrading to HBase 0.90.x from 0.20.x or 0.89.x

You cannot skip major verisons upgrading. If you are upgrading from - version 0.20.x to 0.92.x, you must first go from 0.20.x to 0.90.x and then go - from 0.90.x to 0.92.x.

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Chapter 3. Upgrading

Table of Contents

3.1. HBase version numbers

3.1.1. Odd/Even Versioning or "Development"" Series Releases

3.2. Upgrading from 0.94.x to 0.96.x

3.3. Upgrading from 0.92.x to 0.94.x

3.4. Upgrading from 0.90.x to 0.92.x

3.4.1. You can’t go back! +
3.4.2. MSLAB is ON by default +
3.4.3. Distributed splitting is on by default +
3.4.4. Memory accounting is different now +
3.4.5. On the Hadoop version to use +
3.4.6. HBase 0.92.0 ships with ZooKeeper 3.4.2 +
3.4.7. Online alter is off by default +
3.4.8. WebUI +
3.4.9. Security tarball +
3.4.10. Experimental off-heap cache +
3.4.11. Changes in HBase replication +
3.4.12. RegionServer now aborts if OOME +
3.4.13. HFile V2 and the “Bigger, Fewer” Tendency +

3.5. Upgrading to HBase 0.90.x from 0.20.x or 0.89.x

You cannot skip major verisons upgrading. If you are upgrading from + version 0.90.x to 0.94.x, you must first go from 0.90.x to 0.92.x and then go + from 0.92.x to 0.94.x.

Review Chapter 2, Apache HBase (TM) Configuration, in particular the section on Hadoop version. -

3.1. Upgrading from 0.94.x to 0.96.x

The Singularity

You will have to stop your old 0.94 cluster completely to upgrade. If you are replicating - between clusters, both clusters will have to go down to upgrade. Make sure it is a clean shutdown - so there are no WAL files laying around (TODO: Can 0.96 read 0.94 WAL files?). Make sure - zookeeper is cleared of state. All clients must be upgraded to 0.96 too. -

The API has changed in a few areas; in particular how you use coprocessors (TODO: MapReduce too?) -

TODO: Write about 3.4 zk ensemble and multi support

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\ No newline at end of file Modified: hbase/hbase.apache.org/trunk/book/versions.html URL: http://svn.apache.org/viewvc/hbase/hbase.apache.org/trunk/book/versions.html?rev=1463652&r1=1463651&r2=1463652&view=diff ============================================================================== --- hbase/hbase.apache.org/trunk/book/versions.html (original) +++ hbase/hbase.apache.org/trunk/book/versions.html Tue Apr 2 18:06:19 2013 @@ -1,6 +1,6 @@ - 5.8. Versions

5.8. Versions
Prev	Chapter 5. Data Model	Next

< /div>

5.8. Versions

A {row, column, version} tuple exactly + 5.8. Versions

5.8. Versions
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< /div>

5.8. Versions

A {row, column, version} tuple exactly specifies a cell in HBase. It's possible to have an unbounded number of cells where the row and column are the same but the cell address differs only in its version dimension.

While rows and column keys are expressed as bytes, the version is @@ -14,10 +14,10 @@ first.

There is a lot of confusion over the semantics of cell versions, in HBase. In particular, a couple questions that often come up are:

If multiple writes to a cell have the same version, are all - versions maintained or just the last?^[13]
Is it OK to write cells in a non-increasing version - order?^[14]

Below we describe how the version dimension in HBase currently - works^[15].

5.8.1. Versions and HBase Operations

In this section we look at the behavior of the version dimension - for each of the core HBase operations.

5.8.1.1. Get/Scan

Gets are implemented on top of Scans. The below discussion of + versions maintained or just the last?^[13]

Is it OK to write cells in a non-increasing version + order?^[14]

Below we describe how the version dimension in HBase currently + works^[15].

5.8.1. Versions and HBase Operations

In this section we look at the behavior of the version dimension + for each of the core HBase operations.

5.8.1.1. Get/Scan

Gets are implemented on top of Scans. The below discussion of Get applies equally to Scans.

By default, i.e. if you specify no explicit version, when doing a get, the cell whose version has the largest value is returned (which may or may not be the latest one @@ -45,7 +45,7 @@ Result r = htable.get(get); byte[] b = r.getValue(CF, ATTR); // returns current version of value List<KeyValue> kv = r.getColumn(CF, ATTR); // returns all versions of this column

5.8.1.4. Put

Doing a put always creates a new version of a +

5.8.1.4. Put

Doing a put always creates a new version of a cell, at a certain timestamp. By default the system uses the server's currentTimeMillis, but you can specify the version (= the long integer) yourself, on a @@ -75,7 +75,7 @@ htable.put(put); It's usually best to avoid setting this timestamp yourself. Prefer using a separate timestamp attribute of the row, or have the timestamp a part of the rowkey, or both.

5.8.1.5. Delete

There are three different types of internal delete markers - ^[16]: + ^[16]:

Delete: for a specific version of a column.
Delete column: for all versions of a column.
Delete family: for all columns of a particular ColumnFamily

When deleting an entire row, HBase will internally create a tombstone for each ColumnFamily (i.e., not each individual column).

Deletes work by creating tombstone @@ -87,13 +87,13 @@ htable.put(put); example a delete will not immediately delete (or mark as deleted) the entries in the storage file that correspond to the delete condition. Rather, a so-called tombstone is - written, which will mask the deleted values^[17]. If the version you specified when deleting a row is + written, which will mask the deleted values^[17]. If the version you specified when deleting a row is larger than the version of any value in the row, then you can consider the complete row to be deleted.

For an informative discussion on how deletes and versioning interact, see the thread Put w/ timestamp -> Deleteall -> Put w/ timestamp fails - up on the user mailing list.

Also see Section 9.7.5.4, “KeyValue” for more information on the internal KeyValue format. -

5.8.2. Current Limitations

5.8.2.1. Deletes mask Puts

Deletes mask puts, even puts that happened after the delete - was entered^[18]. Remember that a delete writes a tombstone, which only + up on the user mailing list.

Also see Section 9.7.6.4, “KeyValue” for more information on the internal KeyValue format. +

5.8.2. Current Limitations

5.8.2.1. Deletes mask Puts

Deletes mask puts, even puts that happened after the delete + was entered^[18]. Remember that a delete writes a tombstone, which only disappears after then next major compaction has run. Suppose you do a delete of everything <= T. After this you do a new put with a timestamp <= T. This put, even if it happened after the delete, @@ -104,22 +104,22 @@ htable.put(put); always-increasing versions for new puts to a row. But they can occur even if you do not care about time: just do delete and put immediately after each other, and there is some chance they happen - within the same millisecond.

5.8.2.2. Major compactions change query results

“...create three cell versions at t1, t2 and t3, with a + within the same millisecond.

5.8.2.2. Major compactions change query results

“...create three cell versions at t1, t2 and t3, with a maximum-versions setting of 2. So when getting all versions, only the values at t2 and t3 will be returned. But if you delete the version at t2 or t3, the one at t1 will appear again. Obviously, once a major compaction has run, such behavior will not be the case - anymore...^[19]”

^[13]Currently, only the last written is fetchable.

^[14]Yes

^[15]See HBASE-2406 + anymore...^[19]”

^[13]Currently, only the last written is fetchable.

^[14]Yes

^[15]See HBASE-2406 for discussion of HBase versions. Bending time in HBase makes for a good read on the version, or time, dimension in HBase. It has more detail on versioning than is provided here. As of this writing, the limiitation Overwriting values at existing timestamps mentioned in the article no longer holds in HBase. This section is - basically a synopsis of this article by Bruno Dumon.

^[16]See Lars Hofhansl's blog for discussion of his attempt - adding another, Scanning in HBase: Prefix Delete Marker

^[17]When HBase does a major compaction, the tombstones are + basically a synopsis of this article by Bruno Dumon.

^[16]See Lars Hofhansl's blog for discussion of his attempt + adding another, Scanning in HBase: Prefix Delete Marker

^[17]When HBase does a major compaction, the tombstones are processed to actually remove the dead values, together with the - tombstones themselves.

^[18]HBASE-2256

^[19]See Garbage Collection in Bending + tombstones themselves.

^[18] HBASE-2256

^[19]See Garbage Collection in Bending time in HBase