Chinmay Kulkarni created PHOENIX-6141:
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Summary: Ensure consistency between SYSTEM.CATALOG and
SYSTEM.CHILD_LINK
Key: PHOENIX-6141
URL: https://issues.apache.org/jira/browse/PHOENIX-6141
Project: Phoenix
Issue Type: Improvement
Affects Versions: 4.15.0, 5.0.0
Reporter: Chinmay Kulkarni
Fix For: 4.17.0
Before 4.15, "CREATE/DROP VIEW" was an atomic operation since we were issuing
batch mutations on just the 1 SYSTEM.CATALOG region. In 4.15 we introduced
SYSTEM.CHILD_LINK to store the parent->child links and so a CREATE VIEW is no
longer atomic since it consists of 2 separate RPCs (1 to SYSTEM.CHILD_LINK to
add the linking row and another to SYSTEM.CATALOG to write metadata for the new
view).
If the second RPC i.e. the RPC to write metadata to SYSTEM.CATALOG fails after
the 1st RPC has already gone through, there will be an inconsistency between
both metadata tables. We will see orphan parent->child linking rows in
SYSTEM.CHILD_LINK in this case. This can cause the following issues:
# ALTER TABLE calls on the base table will fail
# DROP TABLE without CASCADE will fail
# The upgrade path has calls like UpgradeUtil.upgradeTable() which will fail
# Any metadata consistency checks can be thrown off
# Unnecessary extra storage of orphan links
The first 3 issues happen because we wrongly deduce that a base table has child
views due to the orphan linking rows.
This Jira aims at trying to come up with a way to make mutations among
SYSTEM.CATALOG and SYSTEM.CHILD_LINK an atomic transaction. We can use a
2-phase commit approach like in global indexing or also potentially explore
using a transaction manager.
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