FilterExpression#filter filter out unmatched metrics directly instead of returning EMPTY

Author: weixiang

oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/Analyzer.java

@@ -129,8 +129,7 @@ public void analyse(final ImmutableMap<String, SampleFamily> sampleFamilies) {
         }
         if (filterExpression != null) {
             input = filterExpression.filter(input);
-            boolean empty = input.values().stream().allMatch(s -> s == SampleFamily.EMPTY);
-            if (empty) {
+            if (input.isEmpty()) {
                 if (log.isDebugEnabled()) {
                     log.debug("{} is ignored due to mismatch of filter {}", expression, filterExpression);
                 }

oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/dsl/FilterExpression.java

@@ -20,12 +20,12 @@
 
 import groovy.lang.Closure;
 import groovy.lang.GroovyShell;
+import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 import lombok.ToString;
 import lombok.extern.slf4j.Slf4j;
 
-import static java.util.stream.Collectors.toMap;
-
 @Slf4j
 @ToString(of = {"literal"})
 public class FilterExpression {
@@ -42,10 +42,14 @@ public FilterExpression(final String literal) {
 
     public Map<String, SampleFamily> filter(final Map<String, SampleFamily> sampleFamilies) {
         try {
-            return sampleFamilies.entrySet().stream().collect(toMap(
-                Map.Entry::getKey,
-                it -> it.getValue().filter(filterClosure)
-            ));
+            Map<String, SampleFamily> result = new HashMap<>();
+            for (Map.Entry<String, SampleFamily> entry : sampleFamilies.entrySet()) {
+                SampleFamily afterFilter = entry.getValue().filter(filterClosure);
+                if (!Objects.equals(afterFilter, SampleFamily.EMPTY)) {
+                    result.put(entry.getKey(), afterFilter);
+                }
+            }
+            return result;
         } catch (Throwable t) {
             log.error("failed to run \"{}\"", literal, t);
         }