Initial support for TEXT fields in LOOKUP JOIN condition

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/lookup/QueryList.java

@@ -32,6 +32,7 @@
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 import java.util.function.IntFunction;
 
 /**
@@ -70,7 +71,12 @@ public static QueryList rawTermQueryList(MappedFieldType field, SearchExecutionC
             }
             case BYTES_REF -> offset -> {
                 BytesRefBlock bytesRefBlock = (BytesRefBlock) block;
-                return bytesRefBlock.getBytesRef(offset, new BytesRef());
+                BytesRef value = bytesRefBlock.getBytesRef(offset, new BytesRef());
+                if (field.typeName().equals("text")) {
+                    // Text fields involve case-insensitive contains queries, we need to use lowercase on the term query
+                    return new BytesRef(value.utf8ToString().toLowerCase(Locale.ROOT));
+                }
+                return value;
             };
             case DOUBLE -> {
                 DoubleBlock doubleBlock = ((DoubleBlock) block);

x-pack/plugin/esql/qa/testFixtures/src/main/resources/lookup-join.csv-spec

@@ -461,7 +461,7 @@ language_code:integer | language_name:keyword       | country:keyword
 ;
 
 ###########################################################################
-# nested filed join behavior with languages_nested_fields index
+# nested field join behavior with languages_nested_fields index
 ###########################################################################
 
 joinOnNestedField
@@ -509,6 +509,18 @@ language.id:integer | language.name:text | language.name.keyword:keyword
 1                   | English            | English
 ;
 
+joinOnNestedNestedFieldRowImplicitKeyword
+required_capability: join_lookup_v10
+
+ROW language.name = "English"
+| LOOKUP JOIN languages_nested_fields ON language.name
+| KEEP language.id, language.name, language.name.keyword
+;
+
+language.id:integer | language.name:keyword | language.name.keyword:keyword
+1                   | English               | English
+;
+
 ###############################################
 # Tests with clientips_lookup index
 ###############################################

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/analysis/Verifier.java

@@ -858,7 +858,7 @@ private static void checkJoin(LogicalPlan plan, Set<Failure> failures) {
             for (int i = 0; i < config.leftFields().size(); i++) {
                 Attribute leftField = config.leftFields().get(i);
                 Attribute rightField = config.rightFields().get(i);
-                if (leftField.dataType() != rightField.dataType()) {
+                if (leftField.dataType().noText() != rightField.dataType().noText()) {
                     failures.add(
                         fail(
                             leftField,

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/LookupFromIndexService.java

@@ -80,7 +80,8 @@ protected String getRequiredPrivilege() {
 
     private static void validateTypes(DataType inputDataType, MappedFieldType fieldType) {
         // TODO: consider supporting implicit type conversion as done in ENRICH for some types
-        if (fieldType.typeName().equals(inputDataType.typeName()) == false) {
+        String typeName = fieldType.typeName().equals("text") ? DataType.KEYWORD.typeName() : fieldType.typeName();
+        if (typeName.equals(inputDataType.noText().typeName()) == false) {
             throw new EsqlIllegalArgumentException(
                 "LOOKUP JOIN match and input types are incompatible: match[" + fieldType.typeName() + "], input[" + inputDataType + "]"
             );