Schema validation yadda yake aiki a MongoDB?

Question

IT Interview Practice · Accepted Answer

Duk da MongoDB yana da sassauci na tarmaki, yana goyon bayan **schema validation** a matakin database — bayyana dokoki (obligatory fields, nau'i, takunkuma masu ƙayyade) da dokumente sai su biyaye. Wannan yana ƙara ingancin bayani *a cikin* MongoDB kanta (ba a cikin kodolin aikina kawai), tare da daidaita sassauci da daidaitawa.

## Bayyana dokoki na bincike

```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 yana amfani da **JSON Schema** don bayyana dokoki na bincike — obligatory fields, nau'i, tsarin yanayi, jeri — waɗannan dokoki ake aiwatar da su ta hanyar database lokacin saka ko sabunta dokumente.

## Matakin bincike da ayyuka

```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` yana ƙara dokoki waɗanda ake bincika; `validationAction` yana ƙara ko karvatsa (reject) ko gawar gawar baje.

## Me yasa a bincika a database (maimakon kawai app kawai)?

```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.
```

## Daidaita sassauci da tsari

```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.)
```

## Me yasa ita ta matuwa

Ganin MongoDB schema validation yana da mahimmanci don **daidaita sassauci na MongoDB tare da ingancin bayani**, don haka ita ita sanin gaske ne don gina aikace-aikace na MongoDB masu aminci.
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Bayyana dokoki na bincike

Matakin bincike da ayyuka

Me yasa a bincika a database (maimakon kawai app kawai)?

Daidaita sassauci da tsari

Me yasa ita ta matuwa

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