EntityFieldQuery has been rewritten

Drupal 7:

    $query = new EntityFieldQuery();
    $query->entityCondition('entity_type', 'entity_test');
    $query->entityCondition('langcode', $default_langcode);
    $query->propertyCondition('user_id', $properties[$default_langcode]['user_id'], NULL, 'original');
    $query->propertyCondition('name', $properties[$default_langcode]['name'], NULL, 'original');
    $query->propertyLanguageCondition($default_langcode, NULL, 'original');
    $query->propertyCondition('name', $properties[$langcode]['name'], NULL, 'translation');
    $query->propertyLanguageCondition($langcode, NULL, 'translation');
    $query->fieldCondition($this->field_name, 'value', $field_value, NULL, NULL, 'translation');
    $query->fieldLanguageCondition($this->field_name, $langcode, NULL, NULL, 'translation');
    $query->propertyOrderBy('name', 'ASC', 'original');
    $result = $query->execute();

And $result was a multidimensional array keyed by entity type and entity id with values of pseudo-entities containing id, revision and bundle.

Drupal 8:

    $query = \Drupal::entityQuery('entity_test');
    $default_langcode_group = $query->andConditionGroup()
      ->condition('user_id', $properties[$default_langcode]['user_id'], '=', $default_langcode)
      ->condition('name', $properties[$default_langcode]['name'], '=', $default_langcode);
    $langcode_group = $query->andConditionGroup()
      ->condition('name', $properties[$langcode]['name'], '=', $langcode)
      ->condition("$this->field_name.value", $field_value, '=', $langcode);
    $result = $query
      ->condition('langcode', $default_langcode)
      ->condition($default_langcode_group)
      ->condition($langcode_group)
      ->sort('name', 'ASC', $default_langcode)
      ->execute();

The query now only works on a single entity type.

The result is an array keyed by revision id if the entity type supports revisions and entity id if not. The values are always entity IDs. This allows the result array to be passed to entity_load_multiple.

To convert a query:

• entityCondition previously worked with entity id, revision id, bundle and entity_type. Now entity_type is passed to the entity_query factory function and the rest can be converted into property queries on the base table.
• propertyCondition calls can be changed to condition calls without any change.
• fieldCondition($field_name, $property_name, $value, $operator) becomes condition("$field_name.$property_name", $value, $operator).
• fieldDeltaCondition($field_name, $value, $operator) calls now can be written as conditon("$field_name.%delta", $value, $operator). Also, delta values can be added to any condition: condition("$field_name.$delta.$property_name", $value, $operator) where $delta is a numeric value.

Same for sorts. Delta and language grouping is deprecated in favor of simply creating andConditionGroup orConditionGroup.