Sergey Shelukhin created HBASE-8340:
---------------------------------------
Summary: WAL log compression handling of seeks seems to be either
inefficient or incorrect
Key: HBASE-8340
URL: https://issues.apache.org/jira/browse/HBASE-8340
Project: HBase
Issue Type: Bug
Reporter: Sergey Shelukhin
In next(...):
{code}
if (compressionContext != null && emptyCompressionContext) {
emptyCompressionContext = false;
}
return ...
{code}
In seek()
{code}
if (compressionContext != null && emptyCompressionContext) {
while (next() != null) {
if (getPosition() == pos) {
emptyCompressionContext = false;
break;
}
}
...
reader.seek(pos);
{code}
So, seek will seek the file directly if either any next, or any seek, has been
called before.
I am not sure what this code is for, but my best guess is that it is to
populate the dictionary for compression.
If it is so, it would seem that one next() call (or even one seek() call) would
not be enough, and seek must always use next(), otherwise it is incorrect.
If we assume that one next() is enough to be able to use reader.seek, as the
current code would seem to imply, then there's no need for the first seek to
call next() in a loop - it can call next once and then do reader.seek.
Note: even in case if all of this works fine because external usage creates the
object and does one seek before any next-s, and no seeks after (the only
bug-free pattern currently possible with both methods used if I'm not
mistaken), then the code needs to be tightened and bug potential removed.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
