ESQL: Add nulls support to Categorize

[ivancea]

Handle nulls and empty strings (Which resolve to null) on Categorize grouping function.

Also, implement seenGroupIds(), which would fail some queries with nulls otherwise.

[elasticsearchmachine]

Hi @ivancea, I've created a changelog YAML for you.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[Copilot]

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 suggestions.

Files not reviewed (1)

• x-pack/plugin/esql/qa/testFixtures/src/main/resources/categorize.csv-spec: Language not supported

Comments skipped due to low confidence (6)

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/CategorizeRawBlockHash.java:67

• [nitpick] The change from static to final for the CategorizeEvaluator class may be unintended. If this class is intended to be nested within another class without requiring an instance of the outer class, it should remain static.

public final class CategorizeEvaluator implements Releasable { 

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/CategorizeRawBlockHash.java:64

• The close method should also handle the seenNull variable if it is used to track state. Ensure that any state variables are reset or handled appropriately when closing resources.

@Override public void close() { categorizer.close(); } 

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/CategorizeRawBlockHash.java:126

• Ensure that the eval method is covered by tests, especially for cases where null values are encountered and handled by the process method.

public IntVector eval(int positionCount, BytesRefVector vVector) { 

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/CategorizedIntermediateBlockHash.java:83

• The increment of category IDs by 1 could cause confusion. Ensure this is intentional and document the reasoning.

idMap.put(oldCategoryId + 1, newCategoryId + 1); 

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/categorization/TokenListCategorizer.java:119

• Ensure that the new behavior introduced by handling nulls in computeCategory is covered by tests.

public TokenListCategory computeCategory(String s, CategorizationAnalyzer analyzer) { 

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/categorization/TokenListCategorizer.java:128

• Ensure that the new behavior introduced by handling nulls in computeCategory is covered by tests.

public TokenListCategory computeCategory(TokenStream ts, int unfilteredStringLen, long numDocs) throws IOException { 

[jan-elastic]

LGTM

[elasticsearchmachine]

💔 Backport failed

Status	Branch	Result
❌	8.x	Commit could not be cherrypicked due to conflicts

You can use sqren/backport to manually backport by running backport --upstream elastic/elasticsearch --pr 117655

[alex-spies]

I know I'm late to the party, but LGTM and thanks @ivancea !