How to fix 'The provided key element does not match the schema' error?

Question

I want to get items that match one of the keys in an array using this code:

```
exports.handler = async (event) => {

try {
        const IDs = 
        [
            {"profileID": {"S": "my_first_id"}}, 
            {"profileID": {"S": "my_second_id"}}
        ]

const postsResult = await db.batchGetItem({
          RequestItems: {
            'Feed': {
              Keys: IDs
            }
          }
        }).promise();

return {
            statusCode: 200,
            body: JSON.stringify(postsResult),
        };
    } catch (err) {
        console.log(err)
        return { error: err }
    }
}
```

But I am getting this error :

> The provided key element does not match the schema

This is the schema:

```
type Feed @model @auth(rules: [{allow: private}]){
  profileID: String @index(name: "feedByProfileID")
  type: String
  postID: String
  shareID: String
  likeID: String
  commentID: String
  replyID: String
}
```

Answer

My assumption is you are trying to do a `BatchGetItem` on a Global Secondary Index (GSI) which is not possible, this is because items in a GSI are not required to be unique, however, they are required to be unique for `GetItem` and `BatchGetItem`.

You can do one of 2 things:
1. Send multiple `Query` calls
2. Send a PartiQL `ExecuteStatement` call

```
// Declare function
const exStatement = statement => {
  db.executeStatement({
    Statement: statement
  })
    .promise() // Promise
    .then(res => {
      console.log(JSON.stringify(res)) 
    })
    .catch(err => console.log(err)) 
}

//Call function
exStatement(`SELECT * from "Feed"."feedByProfileID" where profileID IN ['my_first_id','my_second_id']`) // Up to 50 PK's
```

How to fix 'The provided key element does not match the schema' error?

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