On 2/28/2013 9:11 AM, Mike Matrigali wrote:
In BackingStoreHashTableFromScan I see.
this.max_inmemory_rowcnt = max_inmemory_rowcnt;
if( max_inmemory_rowcnt > 0)
max_inmemory_size = Long.MAX_VALUE;
else
max_inmemory_size = Runtime.getRuntime().totalMemory()/100;
I have been reading the comments and trying to make sense of the logic
and understand all that is happening with max_inmemory_size. I don't
have a test case that goes through the else part of the condition above.
One thing I did notice is that Runtime.getRuntime().totalMemory()
returns really different things if -Xms is set large, for example with
nothing else going on with -Xms1048m -Xmx1048m I get:
Total Memory:1098907648 Free Memory:1088915600
With just -Xmx1048m
Total Memory:4194304 Free Memory:2750304
Two questions
1) Might hash joins use an unexpectedly large amount of memory if -Xms
is set large? I know at the user site where this was being set, they
were setting -Xms in the hopes of optimizing memory usage but I wonder
if it actually increased the amount of memory used by hash joins.
2) Is there a test case that goes through the else clause above that I
could use for my experimentation?
Thanks
Kathey
