fix: optimize existsById() to use Redis EXISTS command instead of data retrieval (#657)

The existsById() method in both RedisDocumentRepository and RedisEnhancedRepository
was inefficiently retrieving entire data structures when only existence validation
was needed. This optimization replaces the inherited Spring Data behavior with
direct Redis EXISTS commands, providing significant performance gains.

Changes:
- Override existsById() in SimpleRedisDocumentRepository and SimpleRedisEnhancedRepository
- Use connection.keyCommands().exists() for O(1) existence checks
- Properly handle composite IDs by implementing getKeyForId() helper methods
- Apply ID filters and maintain full backward compatibility

Performance impact:
- Documents: existsById() → findById() → JSON.GET → full document deserialization
- Hashes: existsById() → findById() → HGETALL → full hash retrieval
- After: existsById() → EXISTS → boolean result only
- Eliminates unnecessary network transfer and CPU overhead for existence checks

Author: bsbodden

redis-om-spring/src/main/java/com/redis/om/spring/repository/support/SimpleRedisDocumentRepository.java

@@ -32,6 +32,7 @@
 import org.springframework.data.keyvalue.core.KeyValueOperations;
 import org.springframework.data.keyvalue.core.mapping.KeyValuePersistentEntity;
 import org.springframework.data.keyvalue.repository.support.SimpleKeyValueRepository;
+import org.springframework.data.redis.core.RedisCallback;
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.data.redis.core.TimeToLive;
 import org.springframework.data.redis.core.convert.KeyspaceConfiguration;
@@ -722,6 +723,50 @@ public <S extends T> boolean exists(Example<S> example) {
     return count(example) > 0;
   }
 
+  @Override
+  public boolean existsById(ID id) {
+    Assert.notNull(id, "The given id must not be null");
+
+    // Use direct Jedis EXISTS command for optimal performance
+    // Construct key properly for composite IDs
+    String fullKey = getKeyForId(id);
+
+    return Boolean.TRUE.equals(modulesOperations.template().execute((RedisCallback<Boolean>) connection -> connection
+        .keyCommands().exists(fullKey.getBytes())));
+  }
+
+  private String getKeyForId(Object id) {
+    // Get the mapping context's entity info
+    RedisEnhancedPersistentEntity<?> persistentEntity = (RedisEnhancedPersistentEntity<?>) mappingContext
+        .getRequiredPersistentEntity(metadata.getJavaType());
+
+    String stringId;
+
+    // Handle composite IDs
+    if (persistentEntity.isIdClassComposite()) {
+      BeanWrapper wrapper = new DirectFieldAccessFallbackBeanWrapper(id);
+      List<String> idParts = new ArrayList<>();
+      for (RedisPersistentProperty idProperty : persistentEntity.getIdProperties()) {
+        Object propertyValue = wrapper.getPropertyValue(idProperty.getName());
+        if (propertyValue != null) {
+          idParts.add(propertyValue.toString());
+        }
+      }
+      stringId = String.join(":", idParts);
+    } else {
+      stringId = mappingConverter.getConversionService().convert(id, String.class);
+    }
+
+    // Apply ID filters if they exist
+    var maybeIdentifierFilter = indexer.getIdentifierFilterFor(metadata.getJavaType());
+    if (maybeIdentifierFilter.isPresent()) {
+      IdentifierFilter<String> filter = (IdentifierFilter<String>) maybeIdentifierFilter.get();
+      stringId = filter.filter(stringId);
+    }
+
+    return getKeyspace() + stringId;
+  }
+
   // -------------------------------------------------------------------------
   // Query By Example Fluent API - QueryByExampleExecutor
   // -------------------------------------------------------------------------

redis-om-spring/src/main/java/com/redis/om/spring/repository/support/SimpleRedisEnhancedRepository.java

@@ -22,6 +22,7 @@
 import org.springframework.data.keyvalue.core.mapping.KeyValuePersistentEntity;
 import org.springframework.data.keyvalue.repository.support.SimpleKeyValueRepository;
 import org.springframework.data.redis.core.PartialUpdate;
+import org.springframework.data.redis.core.RedisCallback;
 import org.springframework.data.redis.core.RedisTemplate;
 import org.springframework.data.redis.core.convert.RedisData;
 import org.springframework.data.redis.core.convert.ReferenceResolverImpl;
@@ -596,6 +597,50 @@ public <S extends T> boolean exists(Example<S> example) {
     return count(example) > 0;
   }
 
+  @Override
+  public boolean existsById(ID id) {
+    Assert.notNull(id, "The given id must not be null");
+
+    // Use direct Jedis EXISTS command for optimal performance
+    // Construct key properly for composite IDs
+    String fullKey = getKeyForId(id);
+
+    return Boolean.TRUE.equals(modulesOperations.template().execute((RedisCallback<Boolean>) connection -> connection
+        .keyCommands().exists(fullKey.getBytes())));
+  }
+
+  private String getKeyForId(Object id) {
+    // Get the mapping context's entity info
+    RedisEnhancedPersistentEntity<?> persistentEntity = (RedisEnhancedPersistentEntity<?>) mappingConverter
+        .getMappingContext().getRequiredPersistentEntity(metadata.getJavaType());
+
+    String stringId;
+
+    // Handle composite IDs
+    if (persistentEntity.isIdClassComposite()) {
+      BeanWrapper wrapper = new DirectFieldAccessFallbackBeanWrapper(id);
+      List<String> idParts = new ArrayList<>();
+      for (RedisPersistentProperty idProperty : persistentEntity.getIdProperties()) {
+        Object propertyValue = wrapper.getPropertyValue(idProperty.getName());
+        if (propertyValue != null) {
+          idParts.add(propertyValue.toString());
+        }
+      }
+      stringId = String.join(":", idParts);
+    } else {
+      stringId = mappingConverter.getConversionService().convert(id, String.class);
+    }
+
+    // Apply ID filters if they exist
+    var maybeIdentifierFilter = indexer.getIdentifierFilterFor(metadata.getJavaType());
+    if (maybeIdentifierFilter.isPresent()) {
+      IdentifierFilter<String> filter = (IdentifierFilter<String>) maybeIdentifierFilter.get();
+      stringId = filter.filter(stringId);
+    }
+
+    return getKeyspace() + stringId;
+  }
+
   // -------------------------------------------------------------------------
   // Query By Example Fluent API - QueryByExampleExecutor
   // -------------------------------------------------------------------------