[jira] [Created] (FLINK-40776) PARSE_URL compiles the query-parameter pattern on every row

["Utkarsh Vashishtha (Jira)" <ji...@apache.org>]

Utkarsh Vashishtha created FLINK-40776:
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             Summary: PARSE_URL compiles the query-parameter pattern on every row
                 Key: FLINK-40776
                 URL: https://issues.apache.org/jira/browse/FLINK-40776
             Project: Flink
          Issue Type: Improvement
          Components: Table SQL / Runtime
            Reporter: Utkarsh Vashishtha


{{SqlFunctionUtils.parseUrl(urlStr, partToExtract, key)}} compiles a new {{Pattern}} on every invocation:
{code:java}
Pattern p = Pattern.compile("(&|^)" + Pattern.quote(key) + "=([^&]*)");
{code}
The pattern depends only on {{{}key{}}}. The URL parse immediately above already goes through {{{}URL_CACHE{}}}.
h3. Fix

Route the pattern through a {{ThreadLocalCache}} keyed on {{{}key{}}}, matching {{URL_CACHE}} in the same class:
{code:java}
private static final ThreadLocalCache<String, Pattern> QUERY_PARAM_PATTERN_CACHE =
        ThreadLocalCache.of(k -> Pattern.compile("(&|^)" + Pattern.quote(k) + "=([^&]*)"));
{code}
 

This fix already runs in our Flink fork and performance benchmarks show an improvement ranging till 4x, depending on key being static (most common / highest improvement) v/s dynamic (dependent on cardinality). 


Found while investigating per-row regex costs in a production Flink SQL deployment.



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