---

name: db-explore description: MongoDB database exploration for understanding game data, debugging, and investigation. Auto-applies when discussing database structure or debugging data issues. allowed-tools: Bash, Read

DB Explore Skill

MongoDB exploration for OpenCivilizations game.

Database Collections

Collection	Purpose
users	Player accounts and authentication
bases	Player base layouts and buildings
clans	Alliance/clan data
battles	Battle replays and results
leaderboards	Rankings cache

MongoDB Shell Commands

Connect

mongosh "mongodb://localhost:27017/dominations"

List Collections

db.getCollectionNames()

Sample Documents

// Get sample user
db.users.findOne()

// Get sample base with buildings
db.bases.findOne({}, { buildings: { $slice: 5 } })

// Get recent battles
db.battles.find().sort({ createdAt: -1 }).limit(5)

Count Documents

// Total users
db.users.countDocuments()

// Active players (last 7 days)
db.users.countDocuments({ lastLogin: { $gte: new Date(Date.now() - 7*24*60*60*1000) } })

Find Documents

// Find user by name
db.users.findOne({ username: "player1" })

// Find bases with specific building
db.bases.find({ "buildings.type": "townCenter" })

// Find clan members
db.clans.findOne({ name: "Warriors" }, { members: 1 })

Aggregations

// Count buildings by type across all bases
db.bases.aggregate([
  { $unwind: "$buildings" },
  { $group: { _id: "$buildings.type", count: { $sum: 1 } } },
  { $sort: { count: -1 } }
])

// Average resources per player
db.users.aggregate([
  { $group: {
    _id: null,
    avgGold: { $avg: "$resources.gold" },
    avgFood: { $avg: "$resources.food" }
  }}
])

Common Queries

Player Investigation

// Get player with full base
db.users.aggregate([
  { $match: { username: "player1" } },
  { $lookup: {
    from: "bases",
    localField: "_id",
    foreignField: "userId",
    as: "base"
  }}
])

Battle Analysis

// Get battle with attacker and defender info
db.battles.aggregate([
  { $match: { _id: ObjectId("...") } },
  { $lookup: { from: "users", localField: "attackerId", foreignField: "_id", as: "attacker" } },
  { $lookup: { from: "users", localField: "defenderId", foreignField: "_id", as: "defender" } }
])

Leaderboard

// Top 10 by trophies
db.users.find({}, { username: 1, trophies: 1 })
  .sort({ trophies: -1 })
  .limit(10)

Important Notes

• Read-only - Never modify production data
• Use limits - Large collections need .limit()
• Index awareness - Check indexes before heavy queries
• Redis for sessions - Active game state is in Redis, not MongoDB