Impala Public Jenkins has submitted this change and it was merged. Change subject: IMPALA-4829: Change default Kudu read behavior for "RYW" ......................................................................
IMPALA-4829: Change default Kudu read behavior for "RYW" Currently the default Kudu read mode is set to "READ_LATEST", which essentially provides no guarantees on reading except that any read issued will read the latest value that the target replica happens to have. This is not necessarily a time after a previous write operation in the same session. By changing the read mode to the misleadingly named "READ_AT_SNAPSHOT", we can ensure that Kudu reads will all be at times at least or greater than the latest "observed" time (which Impala already sets on the client). Note that this does not mean all reads are performed at the same timestamp (i.e. a snapshot read) because that requires setting a snapshot timestamp, but doing this will require more work in the future in both Impala and (mostly) Kudu. The Kudu team calls this "Read Your Writes". This means that, after this change, values written within a session will always be visible to subsequent reads. Before this change, this was usually the case but not guaranteed. Testing: Private test run, running an exhaustive job now. This is otherwise difficult to validate in new tests. This has plenty of time to bake for 2.9 in case we discover performance or functional issues. Change-Id: I4011f8277083982aee2c6c2bfca2f4ae2f8cb31e Reviewed-on: http://gerrit.cloudera.org:8080/5802 Reviewed-by: Thomas Tauber-Marshall <tmarsh...@cloudera.com> Reviewed-by: Dan Hecht <dhe...@cloudera.com> Tested-by: Impala Public Jenkins --- M be/src/exec/kudu-scanner.cc 1 file changed, 7 insertions(+), 7 deletions(-) Approvals: Impala Public Jenkins: Verified Thomas Tauber-Marshall: Looks good to me, but someone else must approve Dan Hecht: Looks good to me, approved -- To view, visit http://gerrit.cloudera.org:8080/5802 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-MessageType: merged Gerrit-Change-Id: I4011f8277083982aee2c6c2bfca2f4ae2f8cb31e Gerrit-PatchSet: 2 Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-Owner: Matthew Jacobs <m...@cloudera.com> Gerrit-Reviewer: Dan Hecht <dhe...@cloudera.com> Gerrit-Reviewer: Impala Public Jenkins Gerrit-Reviewer: Thomas Tauber-Marshall <tmarsh...@cloudera.com>