Swift & Parse：查询Issues类WorkGroup列与Users类WorkGroup列相等的结果

Hey there! Let’s work through this problem together. You’re trying to fetch records where the WorkGroup value in the Issues class matches the same value in the Users class, and you’ve already tried a bunch of methods without luck—let’s break down the right approaches based on exactly what you need.

Scenario 1: Get All Issues That Have a Matching WorkGroup in Users #

If your goal is to retrieve every Issue where its WorkGroup exists in at least one User record, this is straightforward with a subquery and containedIn:

// First, create a query to grab all WorkGroup values from Users
const userWorkGroupQuery = new Parse.Query("Users");
userWorkGroupQuery.select("WorkGroup"); // Only fetch the WorkGroup column to optimize performance

// Now query Issues where WorkGroup is in the set of User WorkGroups
const matchingIssuesQuery = new Parse.Query("Issues");
matchingIssuesQuery.containedIn("WorkGroup", userWorkGroupQuery);

// Run the query
matchingIssuesQuery.find()
  .then(matchingIssues => {
    // Handle your list of matching Issues here
    console.log(`Found ${matchingIssues.length} matching issues`);
  })
  .catch(error => {
    console.error("Error fetching matching issues:", error);
  });

Scenario 2: Get Paired Issues and Users with the Same WorkGroup #

If you need to see which Issues correspond to which Users via matching WorkGroup values, an aggregation query is the way to go. This groups records by WorkGroup and pulls in related data from both classes:

// Define the aggregation pipeline
const pipeline = [
  // Group Issues by WorkGroup and collect all related Issue records
  {
    "$group": {
      "_id": "$WorkGroup",
      "relatedIssues": { "$push": "$$ROOT" }
    }
  },
  // Join with the Users class to pull in Users with the same WorkGroup
  {
    "$lookup": {
      "from": "Users",
      "localField": "_id",
      "foreignField": "WorkGroup",
      "as": "relatedUsers"
    }
  }
];

// Execute the aggregation (you might need a cloud function for this in Parse)
Parse.Cloud.run("getWorkGroupMatches", { pipeline })
  .then(results => {
    // Each result entry has a WorkGroup, its Issues, and its Users
    results.forEach(group => {
      console.log(`WorkGroup: ${group._id}`);
      console.log(`Issues: ${group.relatedIssues.length}`);
      console.log(`Users: ${group.relatedUsers.length}`);
    });
  })
  .catch(error => {
    console.error("Error running aggregation:", error);
  });

Common Pitfalls You Might Have Hit #

• Mismatched Field Types: Double-check that WorkGroup is the same data type (string, number, etc.) in both the Issues and Users classes—type mismatches will silently fail to return matches.
• Incorrect matchesQuery Usage: matchesQuery is designed for pointer relationships (e.g., an Issue has a user pointer to a User), not for matching field values across unrelated classes. containedIn with a subquery is the right tool here.
• Missing Indexes: If you’re working with large datasets, add an index to the WorkGroup field in both classes to speed up your queries.

内容的提问来源于stack exchange，提问作者klykins