Will Berkeley has submitted this change and it was merged. ( http://gerrit.cloudera.org:8080/10213 )
Change subject: Fast path scanning blocks of deleted rows ...................................................................... Fast path scanning blocks of deleted rows This adds some very simple fast-paths in the case that an entire row block consists of rows that were deleted. The first is in the block materialization code: if delta application results in all rows being deleted, we don't need to move forward and materialize any columns. The second is before serializing scan responses to the client. In this case we don't need to loop over each column and read the selection vector for each column. Instead we can just return immediately. I tested this on a table where I'd inserted a few billion rows, deleted them all, and then re-inserted them. Before the patch, a simple 'SELECT * FROM t LIMIT 10' took 306sec. With the first optimization only, it took about 10 seconds. With the second one as well, it took about 2.2 seconds. There are probably more general optimizations that could be done for sparsely-populated RowBlocks (eg where just a few rows are selected) but they are much more complex, and it's relatively common for users to delete large consecutive runs of rows. For example, users may use 'DELETE' all rows in a table or partition before re-adding them, or they may delete all data corresponding to some prefix of the PK. Change-Id: I9fa891c0f4e857ddd1f873ad4855154d078be6b8 Reviewed-on: http://gerrit.cloudera.org:8080/10213 Tested-by: Todd Lipcon <[email protected]> Reviewed-by: Will Berkeley <[email protected]> --- M src/kudu/common/generic_iterators.cc M src/kudu/tserver/tablet_service.cc 2 files changed, 11 insertions(+), 0 deletions(-) Approvals: Todd Lipcon: Verified Will Berkeley: Looks good to me, approved -- To view, visit http://gerrit.cloudera.org:8080/10213 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: kudu Gerrit-Branch: master Gerrit-MessageType: merged Gerrit-Change-Id: I9fa891c0f4e857ddd1f873ad4855154d078be6b8 Gerrit-Change-Number: 10213 Gerrit-PatchSet: 3 Gerrit-Owner: Todd Lipcon <[email protected]> Gerrit-Reviewer: Kudu Jenkins Gerrit-Reviewer: Mostafa Mokhtar <[email protected]> Gerrit-Reviewer: Todd Lipcon <[email protected]> Gerrit-Reviewer: Will Berkeley <[email protected]>
