explain() & Query Performance
db.collection.find(query).explain("executionStats"), DETAILED, INFORMATION, DETA, hai — totalDocsExamined, aur, nReturned, ko, COMPARE, karна, IMPORTANT, hai. AGAR, totalDocsExamined, nReturned, se, KAAFI, ZYAADA, hai, YE, EK, RED, FLAG, hai.
winningPlan, field, mein, DIKHТA, hai, ki, KAUN, sa, STAGE, USE, HUA — "COLLSCAN" (COLLECTION SCAN), MATLAB, INDEX, USE, NAHI, HUA. "IXSCAN" (INDEX SCAN), MATLAB, EK, INDEX, EFFICIENTLY, USE, HUA.
db.users.find({ email: "aarav@example.com" }).explain("executionStats");
// Output mein, check karo:
// executionStats.totalDocsExamined — kitne documents scan hue
// executionStats.nReturned — actual, matching, results
// queryPlanner.winningPlan.stage — "COLLSCAN" (bad) ya "IXSCAN" (good)- explain("executionStats") = query execution, ki, DETAILED, information
- totalDocsExamined vs nReturned = HIGH, difference, RED, FLAG, hai
- COLLSCAN = index, use, nahi, hua. IXSCAN = index, efficiently, use, hua
explain("allPlansExecution"), MongoDB, ke, QUERY, PLANNER, dwara, CONSIDER, kiye, gaye, ALTERNATIVE, plans, bhi, dikhaता hai (rejectedPlans) — YE, samajhne, mein, help, karta, hai, ki, KYUN, EK, PARTICULAR, index, chuna, gaya.
db.users.find({ status: "active", age: { $gt: 18 } }).explain("allPlansExecution");executionTimeMillis, ACTUAL, query, TIME, dikhata hai — LEKIN, TESTING, mein, YE, CACHING, effects, se, MISLEADING, ho, sakta hai. totalDocsExamined, EK, MORE, RELIABLE, indicator, hai, ki, query, ki, EFFICIENCY, KAISI, hai (independent, of, caching).