Schema validation hufanya kazi vipi katika MongoDB?

Question

Accepted Answer

Ingawa MongoDB ni nyumbufu kwa chaguomsingi, inaunga mkono **schema validation** katika kiwango cha database — kufafanua sheria (required fields, types, vikomo vya thamani) ambazo nyaraka zinapaswa kukidhi. Hili linaongeza uadilifu wa data *ndani* ya MongoDB yenyewe (sio tu katika msimbo wa programu), kusawazisha unyumbufu na uthabiti.

## Kufafanua sheria za validation

```js
// add a JSON Schema validator when creating (or modifying) a collection
db.createCollection("users", {
  validator: {
    $jsonSchema: {
      bsonType: "object",
      required: ["name", "email"],            // required fields
      properties: {
        name: { bsonType: "string" },
        email: { bsonType: "string", pattern: "^.+@.+$" },   // type + pattern
        age: { bsonType: "int", minimum: 0, maximum: 120 }   // range
      }
    }
  }
});
// → documents that don't satisfy this are REJECTED on insert/update
```

MongoDB hutumia **JSON Schema** kufafanua sheria za validation — required fields, types, patterns, ranges — zinazotekelezwa na database wakati nyaraka zinapoingizwa au kusasishwa.

## Viwango na vitendo vya validation

```js
db.runCommand({
  collMod: "users",
  validator: { $jsonSchema: { ... } },
  validationLevel: "moderate",     // "strict" (all) or "moderate" (only valid existing docs)
  validationAction: "error"        // "error" (reject) or "warn" (log but allow)
});
```

`validationLevel` hudhibiti nyaraka zipi zinakaguliwa; `validationAction` hudhibiti kama ukiukaji unatoa error (kukataa) au tu kuonya.

## Kwa nini uthibitishe katika database (dhidi ya programu pekee)?

```text
✓ DATABASE-LEVEL guarantee — enforced regardless of which app/code writes data
  (multiple services, scripts, manual changes) → consistent data integrity
✓ A safety net even if application validation is bypassed or buggy
→ Similar reasoning to SQL constraints: the DB is the last line of defense for integrity.
```

## Kusawazisha unyumbufu na muundo

```text
MongoDB's flexibility is valuable, but UNCONTROLLED flexibility → inconsistent data.
Schema validation lets you add structure WHERE you need it:
  → enforce critical fields/types while keeping flexibility elsewhere
  → start flexible, add validation as the schema stabilizes
(Often validation is also/instead done in the app layer, e.g. via Mongoose schemas.)
```

## Kwa nini ni muhimu

Kuelewa schema validation ya MongoDB kuna thamani kwa **kusawazisha unyumbufu wa MongoDB na uadilifu wa data**, hivyo ni maarifa ya manufaa kwa kujenga programu za MongoDB zinazoaminika.

Ingawa unyumbufu usio na schema wa MongoDB ni faida kubwa (unaofaa data inayobadilika na tofauti), **unyumbufu usiodhibitiwa unaweza kusababisha data isiyo thabiti** (fields zilizokosekana, types zisizo sahihi, thamani batili) — wasiwasi halisi kwa ubora wa data.

Schema validation hushughulikia hili kwa kukuruhusu kutekeleza sheria (required fields, types, patterns, ranges kupitia JSON Schema) **katika kiwango cha database**, ili nyaraka zilazimike kuzikidhi.

Thamani muhimu ya **validation ya kiwango-cha-database** (kinyume na ya kiwango-cha-programu pekee) ni kwamba inatekelezwa bila kujali ni programu, service, script, au operesheni ya mkono ipi inayoandika data — kutoa dhamana thabiti ya uadilifu na wavu wa usalama hata kama validation ya programu inakwepwa au ina hitilafu (sababu ile ile kama constraints za SQL: database kama mstari wa mwisho wa ulinzi).

Kuelewa **viwango na vitendo vya validation** (kudhibiti nyaraka zipi zinakaguliwa na kama ukiukaji unakataa au unaonya) kunaruhusu utumiaji nyumbufu.

Muhimu zaidi, kuelewa jinsi ya **kusawazisha unyumbufu na muundo** — kuongeza validation pale uthabiti unapohitajika huku ukibakiza unyumbufu mahali pengine, mara nyingi kuanza nyumbufu na kuongeza validation kadri schema inavyoimarika — kunaonyesha matumizi yaliyokomaa ya MongoDB ambayo hupata faida za unyumbufu bila kupoteza uadilifu muhimu wa data.

Kujua kwamba validation mara nyingi hufanyika katika safu ya programu pia (kwa mfano schemas za Mongoose) pia ni muhimu.

Kwa kuwa uadilifu wa data ni muhimu hata katika databases nyumbufu, na kwa kuwa schema validation ya MongoDB inakuruhusu kutekeleza muundo pale unapohitajika (katika kiwango cha database kwa dhamana imara) huku ukihifadhi unyumbufu, kuelewa schema validation — jinsi inavyofanya kazi, faida za utekelezaji wa kiwango-cha-database, na kusawazisha unyumbufu na muundo — ni maarifa ya thamani na yenye umuhimu wa kivitendo kwa kujenga programu za MongoDB zinazodumisha ubora wa data, uwezo wa manufaa unaoshughulikia wasiwasi wa kawaida wa data isiyo thabiti katika databases zenye schema nyumbufu.