[ES|QL] Enable KQL function as a tech preview (#119730)

Author: afoucret

docs/changelog/119730.yaml

@@ -0,0 +1,5 @@
+pr: 119730
+summary: Enable KQL function as a tech preview
+area: ES|QL
+type: enhancement
+issues: []

docs/reference/esql/esql-limitations.asciidoc

@@ -150,7 +150,7 @@ FROM books
 
 Note that, because of <<esql-limitations-text-fields,the way {esql} treats `text` values>>,
 any queries on `text` fields that do not explicitly use the full-text functions,
-<<esql-match>> or <<esql-qstr>>, will behave as if the fields are actually `keyword` fields:
+<<esql-match>>, <<esql-qstr>> or <<esql-kql>>, will behave as if the fields are actually `keyword` fields:
 they are case-sensitive and need to match the full string.
 
 [discrete]

docs/reference/esql/functions/kibana/definition/kql.json

@@ -18,9 +18,11 @@ See <<esql-limitations-full-text-search,full text search limitations>> for infor
 {esql} supports these full-text search functions:
 
 // tag::search_list[]
+* experimental:[] <<esql-kql>>
 * experimental:[] <<esql-match>>
 * experimental:[] <<esql-qstr>>
 // end::search_list[]
 
+include::layout/kql.asciidoc[]
 include::layout/match.asciidoc[]
 include::layout/qstr.asciidoc[]

docs/reference/esql/functions/search-functions.asciidoc

@@ -155,6 +155,7 @@ static TransportVersion def(int id) {
     public static final TransportVersion TRACK_INDEX_FAILED_DUE_TO_VERSION_CONFLICT_METRIC = def(8_820_00_0);
     public static final TransportVersion REPLACE_FAILURE_STORE_OPTIONS_WITH_SELECTOR_SYNTAX = def(8_821_00_0);
     public static final TransportVersion ELASTIC_INFERENCE_SERVICE_UNIFIED_CHAT_COMPLETIONS_INTEGRATION = def(8_822_00_0);
+    public static final TransportVersion KQL_QUERY_TECH_PREVIEW = def(8_823_00_0);
 
     /*
      * STOP! READ THIS FIRST! No, really,

server/src/main/java/org/elasticsearch/TransportVersions.java

@@ -9,8 +9,6 @@
 
 package org.elasticsearch.rest.action.search;
 
-import org.elasticsearch.Build;
-
 import java.util.HashSet;
 import java.util.Set;
 
@@ -60,9 +58,7 @@ private SearchCapabilities() {}
         capabilities.add(KNN_QUANTIZED_VECTOR_RESCORE);
         capabilities.add(MOVING_FN_RIGHT_MATH);
         capabilities.add(K_DEFAULT_TO_SIZE);
-        if (Build.current().isSnapshot()) {
-            capabilities.add(KQL_QUERY_SUPPORTED);
-        }
+        capabilities.add(KQL_QUERY_SUPPORTED);
         capabilities.add(HIGHLIGHT_MAX_ANALYZED_OFFSET_DEFAULT);
         CAPABILITIES = Set.copyOf(capabilities);
     }

server/src/main/java/org/elasticsearch/rest/action/search/SearchCapabilities.java

@@ -15,10 +15,8 @@
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.xpack.esql.VerificationException;
 import org.elasticsearch.xpack.esql.action.AbstractEsqlIntegTestCase;
-import org.elasticsearch.xpack.esql.action.EsqlCapabilities;
 import org.elasticsearch.xpack.kql.KqlPlugin;
 import org.junit.Before;
-import org.junit.BeforeClass;
 
 import java.util.Collection;
 import java.util.List;
@@ -27,12 +25,6 @@
 import static org.hamcrest.CoreMatchers.containsString;
 
 public class KqlFunctionIT extends AbstractEsqlIntegTestCase {
-
-    @BeforeClass
-    protected static void ensureKqlFunctionEnabled() {
-        assumeTrue("kql function capability not available", EsqlCapabilities.Cap.KQL_FUNCTION.isEnabled());
-    }
-
     @Before
     public void setupIndex() {
         createAndPopulateIndex();

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/plugin/KqlFunctionIT.java

@@ -452,7 +452,7 @@ public enum Cap {
         /**
          * KQL function
          */
-        KQL_FUNCTION(Build.current().isSnapshot()),
+        KQL_FUNCTION,
 
         /**
          * Hash function

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -424,7 +424,10 @@ private static FunctionDefinition[][] functions() {
                 def(MvSum.class, MvSum::new, "mv_sum"),
                 def(Split.class, Split::new, "split") },
             // fulltext functions
-            new FunctionDefinition[] { def(Match.class, bi(Match::new), "match"), def(QueryString.class, uni(QueryString::new), "qstr") } };
+            new FunctionDefinition[] {
+                def(Kql.class, uni(Kql::new), "kql"),
+                def(Match.class, bi(Match::new), "match"),
+                def(QueryString.class, uni(QueryString::new), "qstr") } };
 
     }
 
@@ -434,7 +437,6 @@ private static FunctionDefinition[][] snapshotFunctions() {
                 // The delay() function is for debug/snapshot environments only and should never be enabled in a non-snapshot build.
                 // This is an experimental function and can be removed without notice.
                 def(Delay.class, Delay::new, "delay"),
-                def(Kql.class, uni(Kql::new), "kql"),
                 def(Rate.class, Rate::withUnresolvedTimestamp, "rate"),
                 def(Term.class, bi(Term::new), "term") } };
     }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/EsqlFunctionRegistry.java

@@ -25,10 +25,8 @@ public static List<NamedWriteableRegistry.Entry> getNamedWriteables() {
         entries.add(MultiMatchQueryPredicate.ENTRY);
         entries.add(QueryString.ENTRY);
         entries.add(Match.ENTRY);
+        entries.add(Kql.ENTRY);
 
-        if (EsqlCapabilities.Cap.KQL_FUNCTION.isEnabled()) {
-            entries.add(Kql.ENTRY);
-        }
         if (EsqlCapabilities.Cap.TERM_FUNCTION.isEnabled()) {
             entries.add(Term.ENTRY);
         }