Ingest DateProcessor (small) speedup, optimize collections code in DateFormatter.forPattern

modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/DateProcessor.java

@@ -85,7 +85,7 @@ private ZoneId newDateTimeZone(Map<String, Object> params) {
     }
 
     private Locale newLocale(Map<String, Object> params) {
-        return (locale == null) ? Locale.ROOT : LocaleUtils.parse(locale.newInstance(params).execute());
+        return locale == null ? Locale.ROOT : LocaleUtils.parse(locale.newInstance(params).execute());
     }
 
     @Override

server/src/main/java/org/elasticsearch/common/time/DateFormatter.java

@@ -19,7 +19,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
-import java.util.stream.Collectors;
 
 public interface DateFormatter {
 
@@ -114,14 +113,17 @@ static DateFormatter forPattern(String input, Version supportedVersion) {
             input = input.substring(1);
         }
 
-        List<String> patterns = splitCombinedPatterns(input);
-        List<DateFormatter> formatters = patterns.stream().map(p -> {
+        // forPattern can be hot (e.g. executing a date processor on each document in a 1000 document bulk index request),
+        // so this is a for each loop instead of the equivalent stream pipeline
+        String[] patterns = splitCombinedPatterns(input);
+        List<DateFormatter> formatters = new ArrayList<>(patterns.length);
+        for (String pattern : patterns) {
             // make sure we still support camel case for indices created before 8.0
             if (supportedVersion.before(Version.V_8_0_0)) {
-                return LegacyFormatNames.camelCaseToSnakeCase(p);
+                pattern = LegacyFormatNames.camelCaseToSnakeCase(pattern);
             }
-            return p;
-        }).map(DateFormatters::forPattern).collect(Collectors.toList());
+            formatters.add(DateFormatters.forPattern(pattern));
+        }
 
         if (formatters.size() == 1) {
             return formatters.get(0);
@@ -130,13 +132,12 @@ static DateFormatter forPattern(String input, Version supportedVersion) {
         return JavaDateFormatter.combined(input, formatters);
     }
 
-    static List<String> splitCombinedPatterns(String input) {
-        List<String> patterns = new ArrayList<>();
-        for (String pattern : Strings.delimitedListToStringArray(input, "||")) {
+    static String[] splitCombinedPatterns(String input) {
+        String[] patterns = Strings.delimitedListToStringArray(input, "||");
+        for (String pattern : patterns) {
             if (Strings.hasLength(pattern) == false) {
                 throw new IllegalArgumentException("Cannot have empty element in multi date format pattern: " + input);
             }
-            patterns.add(pattern);
         }
         return patterns;
     }

x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/IndexDeprecationChecks.java

@@ -227,7 +227,7 @@ static DeprecationIssue deprecatedCamelCasePattern(IndexMetadata indexMetadata)
 
     private static boolean isDateFieldWithCamelCasePattern(Map<?, ?> property) {
         if ("date".equals(property.get("type")) && property.containsKey("format")) {
-            List<String> patterns = DateFormatter.splitCombinedPatterns((String) property.get("format"));
+            String[] patterns = DateFormatter.splitCombinedPatterns((String) property.get("format"));
             for (String pattern : patterns) {
                 LegacyFormatNames format = LegacyFormatNames.forName(pattern);
                 return format != null && format.isCamelCase(pattern);
@@ -239,7 +239,7 @@ private static boolean isDateFieldWithCamelCasePattern(Map<?, ?> property) {
     private static String changeFormatToSnakeCase(String type, Map.Entry<?, ?> entry) {
         Map<?, ?> value = (Map<?, ?>) entry.getValue();
         final String formatFieldValue = (String) value.get("format");
-        List<String> patterns = DateFormatter.splitCombinedPatterns(formatFieldValue);
+        String[] patterns = DateFormatter.splitCombinedPatterns(formatFieldValue);
         StringBuilder sb = new StringBuilder(
             "Convert [" + entry.getKey() + "] format [" + formatFieldValue + "] " + "which contains deprecated camel case to snake case. "
         );