ES|QL brute force l2_norm vector function (#132025)

Author: tteofili

docs/reference/query-languages/esql/_snippets/functions/description/v_l2_norm.md

@@ -0,0 +1,90 @@
+ # Tests for l2_norm similarity function
+ 
+ similarityWithVectorField
+ required_capability: l2_norm_vector_similarity_function
+ 
+// tag::vector-l2-norm[]
+ from colors
+ | eval similarity = v_l2_norm(rgb_vector, [0, 255, 255]) 
+ | sort similarity desc, color asc 
+// end::vector-l2-norm[]
+ | limit 10
+ | keep color, similarity
+ ;
+ 
+// tag::vector-l2-norm-result[]
+color:text | similarity:double
+red        | 441.6729431152344
+maroon     | 382.6669616699219
+crimson    | 376.36419677734375
+orange     | 371.68536376953125
+gold       | 362.8360595703125
+black      | 360.62445068359375
+magenta    | 360.62445068359375
+yellow     | 360.62445068359375
+firebrick  | 359.67486572265625
+tomato     | 351.0227966308594
+// end::vector-l2-norm-result[] 
+;
+
+ similarityAsPartOfExpression
+ required_capability: l2_norm_vector_similarity_function
+ 
+ from colors
+ | eval score = round((1 + v_l2_norm(rgb_vector, [0, 255, 255]) / 2), 3) 
+ | sort score desc, color asc 
+ | limit 10
+ | keep color, score
+ ;
+
+color:text | score:double
+red        | 221.836
+maroon     | 192.333
+crimson    | 189.182
+orange     | 186.843
+gold       | 182.418
+black      | 181.312
+magenta    | 181.312
+yellow     | 181.312
+firebrick  | 180.837
+tomato     | 176.511
+;
+
+similarityWithLiteralVectors
+required_capability: l2_norm_vector_similarity_function
+ 
+row a = 1
+| eval similarity = round(v_l2_norm([1, 2, 3], [0, 1, 2]), 3) 
+| keep similarity
+;
+
+similarity:double
+1.732
+;
+
+ similarityWithStats
+ required_capability: l2_norm_vector_similarity_function
+ 
+ from colors
+ | eval similarity = round(v_l2_norm(rgb_vector, [0, 255, 255]), 3) 
+ | stats avg = round(avg(similarity), 3), min = min(similarity), max = max(similarity)
+ ;
+
+avg:double | min:double | max:double
+274.974    | 0.0        | 441.673
+;
+
+# TODO Need to implement a conversion function to convert a non-foldable row to a dense_vector
+similarityWithRow-Ignore
+required_capability: l2_norm_vector_similarity_function
+ 
+row vector = [1, 2, 3] 
+| eval similarity = round(v_l2_norm(vector, [0, 1, 2]), 3) 
+| sort similarity desc, color asc 
+| limit 10
+| keep color, similarity
+;
+
+similarity:double
+0.978  
+;

docs/reference/query-languages/esql/_snippets/functions/examples/v_l2_norm.md

@@ -21,6 +21,7 @@
 import org.elasticsearch.xpack.esql.action.AbstractEsqlIntegTestCase;
 import org.elasticsearch.xpack.esql.action.EsqlCapabilities;
 import org.elasticsearch.xpack.esql.expression.function.vector.L1Norm;
+import org.elasticsearch.xpack.esql.expression.function.vector.L2Norm;
 import org.elasticsearch.xpack.esql.expression.function.vector.VectorSimilarityFunction.SimilarityEvaluatorFunction;
 import org.junit.Before;
 
@@ -47,6 +48,9 @@ public static Iterable<Object[]> parameters() throws Exception {
         if (EsqlCapabilities.Cap.L1_NORM_VECTOR_SIMILARITY_FUNCTION.isEnabled()) {
             params.add(new Object[] { "v_l1_norm", (SimilarityEvaluatorFunction) L1Norm::calculateSimilarity });
         }
+        if (EsqlCapabilities.Cap.L2_NORM_VECTOR_SIMILARITY_FUNCTION.isEnabled()) {
+            params.add(new Object[] { "v_l2_norm", (SimilarityEvaluatorFunction) L2Norm::calculateSimilarity });
+        }
 
         return params;
     }

docs/reference/query-languages/esql/_snippets/functions/layout/v_l2_norm.md

@@ -1322,6 +1322,11 @@ public enum Cap {
          */
         L1_NORM_VECTOR_SIMILARITY_FUNCTION(Build.current().isSnapshot()),
 
+        /**
+         * l2 norm vector similarity function
+         */
+        L2_NORM_VECTOR_SIMILARITY_FUNCTION(Build.current().isSnapshot()),
+
         /**
          * Support for the options field of CATEGORIZE.
          */