xiarixiaoyao edited a comment on pull request #3668:
URL: https://github.com/apache/hudi/pull/3668#issuecomment-921467046
@codope thanks for your review. Let me answer some your questions
first，pls forgive me for being busy today, I need to modify something for the
pr of zorder
**Let's add docs for all the public classes and APIs.**
ok，i will added。
**Does the merge schema action handle evolution of non-leaf fields in nested
fields? For example, if a.b.c is renamed to a.d.c.**
this is a strange demand， if you want to change a.b.c to a.d.c , why donot
use spark.sql(s"alter table ${tableName} rename column a.b to d"). we support
handle all the non-leaf fields.
**IIUC, the patch has not yet handled old or existing schema compatibility
as mentioned in the RFC right?**
already deal with this situation. pls see the TestSpark3DDL, we first
create a table and insert some data to it. now no id-schema is produced. then
we do schema change, and the id-schema is produced. the test result confirmed
this。
**Since schema history is being changed not only at the write time but also
at the read time, so we need to think of both writer and reader concurrency.**
A little doubtful， hudi is snapshot isolated， maybe only need to deal with
concurrency between write and write， if i am wrong pls fix me ， thanks
Now there is the most important question， I now tend to use metatable to
store historical schema。 as we know metatable use hfile to store data， the
hfile has a very good point query performance， what do you suggest？
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