Indexes sunadarta MongoDB?

Question

IT Interview Practice · Accepted Answer

**Indexes** a cikin MongoDB suna sauri gidaje ta hanyar bada dabase damar neman dokumaindi ba tare da tantanta dukan jerin aiki ba — kamar yadda yake a cikin bankaura. Ba tare da indexes ba, gidaje suna yi **collection scan** (tantanta kowane dokumenti); tare da su, neman aiki suna da sauri. MongoDB yana goyan bayan nau'o'in index da yawa.

## Yin da amfani da indexes

```js
// without an index, this scans EVERY document (slow on a big collection)
db.users.find({ email: "ann@x.com" });

// create an index → fast lookups
db.users.createIndex({ email: 1 });        // 1 = ascending (B-tree index)
db.users.find({ email: "ann@x.com" });     // now uses the index

db.users.getIndexes();                      // list indexes
```

Aikin `_id` na gida (default) koyaushe an yi masa index. Kuna ƙara indexes a filayen da kuke bugun gidaje, jera, ko tacewa akai-akai.

## Compound indexes (filayen da yawa)

```js
// a compound index on multiple fields — order matters!
db.users.createIndex({ country: 1, age: -1 });
// helps: { country: ? }, { country: ?, age: ? }  (leftmost prefix)
// does NOT help: { age: ? } alone
```

**Compound indexes** suna rufe gidaje a kan filayen da yawa, amma **tsari na filan yana da muhimmanci** (index yana goyan bayan gidaje ta amfani da sashi na gida na fari — ka muhimmiyar dokoki don fahimta).

## Nau'o'in index

```text
Single field    → { field: 1 }
Compound        → { a: 1, b: -1 } (multiple fields)
Multi-key       → automatically created when indexing an ARRAY field (indexes each element)
Text            → text search on string content
Geospatial      → 2dsphere for location queries
Hashed          → for hashed sharding
TTL             → { createdAt: 1 } with expireAfterSeconds → auto-delete old docs
Unique          → { email: 1 }, { unique: true } → enforce uniqueness
Partial/Sparse  → index only some documents
```

## Musayar hali (kamar SQL)

```text
✓ Indexes speed up reads dramatically (collection scan → index lookup)
✗ But they consume storage and SLOW DOWN writes (each write updates indexes)
→ Index what you query frequently; don't over-index (hurts writes). Use explain()
  to verify queries use indexes (look for COLLSCAN = bad, IXSCAN = good).
```

## Me ya sa wannan ya sa layuka

Indexes daya daga mafi mahimman butun don MongoDB ikon — abin kayan aiki don sauri gidaje, kuma ƙa'idoje sun kasance kamar bankaura, don haka fahimta su aiki da muhimmanci ga aikace-aikacen MongoDB da ke aiki da sauri.

Ba tare da indexes ba, gidaje suna bubugi **collection scans** (tantanta kowane dokumenti — masu rauni sosai yayin da tarjima ke girma), har da indexes suna bada sauri gidaje — sau da yawa bambanci tsakanin gida da ke ɗaukar milliseconds da (sekoki).

Fahimta yadda ake yin indexes a kan filayen da aka bugi akai-akai/jera/tacewa aiki ne gida. **Compound indexes** (rufe gidaje na filayen da yawa) suna da mahimmanci, musamman dokoki cewa **tsari na filan yana da muhimmanci** (index yana goyan bayan gidaje ta amfani da sashi na gida na fari — ka muhimmiyar ga haƙar daneyi compound indexes na tasiri).

Sanin nau'o'in index na MongoDB-relevant yana da daraja: **multi-key indexes** (ta atomatik sauri abubuwan jeri — muhimmanci da aka bayar ga tsarukan MongoDB masu jeri), **TTL indexes** (atomatik-jiya tsofaffin dokumenti — aiki ga yadi, yunƙuri, bayyananniyar bayanai), **unique indexes** (tabbatarwa na musammaniya), rubutun da geospatial indexes don gidaje na musammaniya, da partial/sparse indexes.

Fahimta **musayar hali** (indexes suna sauri karantawa amma suna cin kudin ajiya da sauri rubutu, don haka index abun da kuke bugun ba tare da over-indexing ba) da amfani **`explain()`** don tabbatarwa gidaje suna amfani da indexes (COLLSCAN = rauni scan, IXSCAN = aiki index daidai) ne gawar aiki na mahimmanci don gara daidai.

Tun yayin da jiya ikon yana da mahimmanci kuma daneyi index daidai ita ce mafi tasiri na MongoDB ikon, fahimta indexes — yadda suke aiki, jari na compound index, nau'o'in MongoDB-specific (multi-key, TTL, musammaniya), karantawa/rubutu musayar hali, da tabbatarwa tare da explain() — aiki da girma, darajar sanin ga aiki MongoDB aikace-aikacen da kuma daya daga mafi mahimmiyar butun MongoDB, jara gida mahimmiyar a bankaura bankaura.

Yin da amfani da indexes

Compound indexes (filayen da yawa)

Nau'o'in index

Musayar hali (kamar SQL)

Me ya sa wannan ya sa layuka

Tambayoyi masu alaƙa