Bug fix: Facilitate second retrieval of the same value (#134770)

docs/changelog/134790.yaml

@@ -0,0 +1,6 @@
+pr: 134790
+summary: "Bug fix: Facilitate second retrieval of the same value"
+area: Infra/Core
+type: bug
+issues:
+ - 134770

libs/x-content/impl/src/main/java/org/elasticsearch/xcontent/provider/json/ESUTF8StreamJsonParser.java

@@ -28,6 +28,7 @@
 public class ESUTF8StreamJsonParser extends UTF8StreamJsonParser implements OptimizedTextCapable {
     protected int stringEnd = -1;
     protected int stringLength;
+    protected byte[] lastOptimisedValue;
 
     private final List<Integer> backslashes = new ArrayList<>();
 
@@ -53,6 +54,9 @@ public ESUTF8StreamJsonParser(
     @Override
     public Text getValueAsText() throws IOException {
         if (_currToken == JsonToken.VALUE_STRING && _tokenIncomplete) {
+            if (lastOptimisedValue != null) {
+                return new Text(new XContentString.UTF8Bytes(lastOptimisedValue), stringLength);
+            }
             if (stringEnd > 0) {
                 final int len = stringEnd - 1 - _inputPtr;
                 return new Text(new XContentString.UTF8Bytes(_inputBuffer, _inputPtr, len), stringLength);
@@ -137,6 +141,7 @@ protected Text _finishAndReturnText() throws IOException {
                 copyPtr = backslash + 1;
             }
             System.arraycopy(inputBuffer, copyPtr, buff, destPtr, ptr - copyPtr);
+            lastOptimisedValue = buff;
             return new Text(new XContentString.UTF8Bytes(buff), stringLength);
         }
     }
@@ -146,6 +151,7 @@ public JsonToken nextToken() throws IOException {
         if (_currToken == JsonToken.VALUE_STRING && _tokenIncomplete && stringEnd > 0) {
             _inputPtr = stringEnd;
             _tokenIncomplete = false;
+            lastOptimisedValue = null;
         }
         stringEnd = -1;
         return super.nextToken();
@@ -156,6 +162,7 @@ public boolean nextFieldName(SerializableString str) throws IOException {
         if (_currToken == JsonToken.VALUE_STRING && _tokenIncomplete && stringEnd > 0) {
             _inputPtr = stringEnd;
             _tokenIncomplete = false;
+            lastOptimisedValue = null;
         }
         stringEnd = -1;
         return super.nextFieldName(str);
@@ -166,6 +173,7 @@ public String nextFieldName() throws IOException {
         if (_currToken == JsonToken.VALUE_STRING && _tokenIncomplete && stringEnd > 0) {
             _inputPtr = stringEnd;
             _tokenIncomplete = false;
+            lastOptimisedValue = null;
         }
         stringEnd = -1;
         return super.nextFieldName();

libs/x-content/impl/src/test/java/org/elasticsearch/xcontent/provider/json/ESUTF8StreamJsonParserTests.java

@@ -65,6 +65,10 @@ public void testGetValueAsText() throws IOException {
             var text = parser.getValueAsText();
             assertThat(text, Matchers.notNullValue());
             assertTextRef(text.bytes(), "bar\"baz\"");
+            // Retrieve the value for a second time to ensure the last value is available
+            text = parser.getValueAsText();
+            assertThat(text, Matchers.notNullValue());
+            assertTextRef(text.bytes(), "bar\"baz\"");
         });
 
         testParseJson("{\"foo\": \"b\\u00e5r\"}", parser -> {

rest-api-spec/src/yamlRestTest/resources/rest-api-spec/test/mapping/30_multi_field_keyword.yml

@@ -0,0 +1,45 @@
+---
+Keyword with escaped characters as multi-field:
+  - do:
+      indices.create:
+        index: test
+        body:
+          mappings:
+            properties:
+              foo:
+                type: keyword
+                fields:
+                  bar:
+                    type: keyword
+
+  - do:
+      index:
+        index: test
+        id:    "1"
+        refresh: true
+        body:
+          foo: "c:\\windows\\system32\\svchost.exe"
+
+  - do:
+      search:
+        index: test
+        body:
+          query:
+            term:
+              foo: "c:\\windows\\system32\\svchost.exe"
+
+  - match: { "hits.total.value": 1 }
+  - match:
+      hits.hits.0._source.foo: "c:\\windows\\system32\\svchost.exe"
+
+  - do:
+      search:
+        index: test
+        body:
+          query:
+            term:
+              foo.bar: "c:\\windows\\system32\\svchost.exe"
+
+  - match: { "hits.total.value": 1 }
+  - match:
+      hits.hits.0._source.foo: "c:\\windows\\system32\\svchost.exe"