Query.php

<?php

namespace Drupal\workspaces\EntityQuery;

use Drupal\Core\Entity\Query\Sql\Query as BaseQuery;

/**
 * Alters entity queries to use a workspace revision instead of the default one.
 */
class Query extends BaseQuery {
  use QueryTrait {
    prepare as traitPrepare;
  }
  
  /**
   * {@inheritdoc}
   */
  public function prepare() {
    $this->traitPrepare();
    // If the prepare() method from the trait decided that we need to alter this
    // query, we need to re-define the key fields for fetchAllKeyed() as SQL
    // expressions.
    if ($this->sqlQuery
      ->getMetaData('active_workspace_id')) {
      $id_field = $this->entityType
        ->getKey('id');
      $revision_field = $this->entityType
        ->getKey('revision');
      // Since the query is against the base table, we have to take into account
      // that the revision ID might come from the workspace_association
      // relationship, and, as a consequence, the revision ID field is no longer
      // a simple SQL field but an expression.
      $this->sqlFields = [];
      $this->sqlQuery
        ->addExpression("COALESCE([workspace_association].[target_entity_revision_id], [base_table].[{$revision_field}])", $revision_field);
      $this->sqlQuery
        ->addExpression("[base_table].[{$id_field}]", $id_field);
      $this->sqlGroupBy['workspace_association.target_entity_revision_id'] = 'workspace_association.target_entity_revision_id';
      $this->sqlGroupBy["base_table.{$id_field}"] = "base_table.{$id_field}";
      $this->sqlGroupBy["base_table.{$revision_field}"] = "base_table.{$revision_field}";
    }
    return $this;
  }

}