Qilong Wang created FLINK-39396:
-----------------------------------
Summary: Simplify early return condition in
SqlLikeChainChecker.check()
Key: FLINK-39396
URL: https://issues.apache.org/jira/browse/FLINK-39396
Project: Flink
Issue Type: Technical Debt
Components: Table SQL / Planner
Affects Versions: 2.3.0
Reporter: Qilong Wang
Fix For: 2.3.0
Problem
The early return condition in SqlLikeChainChecker.check() is overly complex and
hard to understand:
{code:java}
if (mark < minLen
|| beginPattern == null
&& endPattern == null
&& middlePatterns.length == 0
&& mark > 0
&& (leftAnchor || rightAnchor)) {
return false;
}{code}
The second branch (after ||) combines 5 sub-conditions, but through analysis,
the only scenario that satisfies all of them is when the pattern is an empty
string and the input is non-empty:
beginPattern == null && endPattern == null && middlePatterns.length == 0: no
literal segments were parsed.
leftAnchor || rightAnchor: the pattern does not start or end with %.
The only pattern that produces zero tokens from StringTokenizer AND has at
least one anchor is the empty string "".
The original comment also reflects this confusion: "the pattern is empty (or
anchored with no literals)" — the two cases described by "or" are actually the
same case.
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