Vihang Karajgaonkar created IMPALA-10468:
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Summary: DROP events which are generated while a batch is being
processed may add table incorrectly
Key: IMPALA-10468
URL: https://issues.apache.org/jira/browse/IMPALA-10468
Project: IMPALA
Issue Type: Improvement
Reporter: Vihang Karajgaonkar
Assignee: Vihang Karajgaonkar
One of the problems with CREATE/DROP events is that they may occur while a
batch is being processed and hence EventsProcessor may not able aware of that.
For example, consider the following sequence of statements:
create table foo (c1 int);
drop table foo;
create table foo (c2 int);
drop table foo;
These statements will generate CREATE_TABLE, DROP_TABLE, CREATE_TABLE,
DROP_TABLE event sequence. Generally, if all these 4 events are fetched in a
batch, then the first CREATE_TABLE and third CREATE_TABLE is ignored because it
is followed by the a DROP_TABLE in the sequence and the DROP_TABLE events take
no effect since the table doesn't exist in catalogd anymore.
However, if the events processor fetches these events in 2 batches (3 and 1)
then after the first batch of CREATE_TABLE, DROP_TABLE, CREATE_TABLE is
processed, the third event will add the table foo in the catalogd. The
subsequent batch's DROP_TABLE will be processed and remove the table, but
between the two batches, catalogd will say that a table called foo exists. This
can lead to statements getting errored out. Eg. a statement like create table
foo (c3 int) after the above statements will error out with a
TableAlreadyExists error.
The problem happens for databases too. So far I have not been able to reproduce
this for Partitions but I don't see why it will not happen with Partitions also.
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