# IRPCVault.GetMetadataStructureItemIdsByAliases_Compressed

Location: [gRPC API](https://developer.m-files.com/APIs/gRPC-API/index.md) > [Vault API](https://developer.m-files.com/APIs/gRPC-API/vault/index.md) > [Vault information](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/index.md)

HTML version: https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/GetMetadataStructureItemIdsByAliases_Compressed/

Badges: `Vault API / core` `read` `session or assertion` `idempotent` `returns metadata structure version`

Gets alias-to-ID mappings of several kinds of metadata structure item as JSON, with the option to
exclude kinds.

- **Service:** [Vault information](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/index.md) `MFiles.IRPCVault`
- **gRPC method:** `/MFiles.IRPCVault/GetMetadataStructureItemIdsByAliases_Compressed`
- **HTTP (mf-http-grpc):** `POST /grpc/v1/get-metadata-structure-item-ids-by-aliases_-compressed`
- **Request:** [`GetMetadataStructureItemIdsByAliases_CompressedRequest`](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/GetMetadataStructureItemIdsByAliases_Compressed/index.md#request)
- **Response:** [`GetMetadataStructureItemIdsByAliases_CompressedResponse`](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/GetMetadataStructureItemIdsByAliases_Compressed/index.md#response)
- **Book and level:** Vault API, core
- **Kind:** read
- **Session:** Required: a session (mfiles-session-id-bin metadata) or a session assertion (x-mf-session-assertion metadata).
- **Idempotent:** yes
- **Returns metadata structure version:** yes (in the mfiles-metadata-version-bin trailer)
- **Streaming:** none (unary)

<a id="remarks"></a>

## Remarks

Works like
[GetMetadataStructureItemIdsByAliases](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/GetMetadataStructureItemIdsByAliases/index.md),
with the same JSON format and compression, but takes lists of kinds. `unambiguous_aliases_only`
must be true. Excluding `METADATA_STRUCTURE_ITEM_ALL` fails with `E_INVALIDARG`.

<a id="request"></a>

## Request: GetMetadataStructureItemIdsByAliases_CompressedRequest

> Nested message fields are expanded to depth 3; follow a type link for deeper levels and for the type's own page.

| Field | Type | Description |
|---|---|---|
| `msi_array_included[]` | repeated [`MetadataStructureItem`](https://developer.m-files.com/APIs/gRPC-API/Reference/Enums/MFiles.MetadataStructureItem/index.md) | The kinds of item to return. A single `METADATA_STRUCTURE_ITEM_ALL` means every kind that can have aliases. |
| `msi_array_excluded` | [`MetadataStructureItemArray`](https://developer.m-files.com/APIs/gRPC-API/Reference/Messages/MFiles.MetadataStructureItemArray/index.md) | Optional. Kinds to leave out, typically together with `METADATA_STRUCTURE_ITEM_ALL` in `msi_array_included`. |
| `msi_array_excluded.value[]` | repeated [`MetadataStructureItem`](https://developer.m-files.com/APIs/gRPC-API/Reference/Enums/MFiles.MetadataStructureItem/index.md) | An array of the MetadataStructureItem values. |
| `unambiguous_aliases_only` | `bool` | Must be true; false fails with `E_NOTIMPL`. |

<a id="response"></a>

## Response: GetMetadataStructureItemIdsByAliases_CompressedResponse

> Nested message fields are expanded to depth 3; follow a type link for deeper levels and for the type's own page.

| Field | Type | Description |
|---|---|---|
| `data` | `bytes` | NUL-terminated UTF-8 JSON, zlib-compressed unless `uncompressed_length` is 4294967295. |
| `uncompressed_length` | `uint32` | Size of the decompressed `data`, or 4294967295 if `data` is not compressed. |

<a id="related"></a>

## Related methods

- [GetMetadataStructureItemIdsByAliases](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/GetMetadataStructureItemIdsByAliases/index.md): Gets all unambiguous alias-to-ID mappings of one kind of metadata structure item, or of all kinds, as JSON.
- [GetMetadataStructure](https://developer.m-files.com/APIs/gRPC-API/Reference/MFiles.IRPCVault/GetMetadataStructure/index.md): Gets the vault's real object types (not value lists), with icons, in one call.