Add delete if exist method

[bidoubiwa]

State of deleting

As for now, to delete an index, one should first be sure the index does not exist already.

Problem

Re-indexing all documents is often slower than deleting the index, and push the documents on a fresh index.
Meaning that this is an operation that is potentially often used by our users (me for example)

Other Motivations

In milli we will be introduced with swap, meilisearch/transplant#28 (see @curquiza response).

Nontheless:

The swap is great, but nonetheless user may still want that method for tests/security/shutdown. It would avoid that in our e2e tests we have to delete all indexes before running the tests (at least in javascript SDK).
It can be used in a teardown method or a onstart as it cleans the instance.
It would avoid having home-made deleteIfExists function in our code that is not tested.

Solution and Vote

We agreed on the necessity of this function. We still have to agree on a naming.

Examples are done using javascript

All in function name 👀

We provide a new function with an explicit naming

client.index("myindex").deleteIfExist()
client.deleteIndexIfExists("myindex")

Pros

No need to search into references to know available parameters.
Only need to see available functions.

Cons

How longer the method name, how unreadable it becomes.

Optionnal parameter 🎉

We provide a new option object to already existing functions.

client.index("myindex").delete({ ifExists: true })
client.deleteIndex("myindex", { ifExists: true })

Pros

No need to create a new function, also more readable.

Cons

Need to know the existence of the options object and which options are available

Return value.

Boolean

If there was a delete, it would return true. If the index did not exist, and thus none have been deleted, it would return false.

const deleteOccured = client.index('myindex').deleteIfExists() // true of false

Index instance

the method would return the instance in itself to let the user chain its actions without having to create a new index object.

Example:

const index = client.index('myindex').deleteIfExists()
index.addDocuments(myDocuments) 

Without this option we have to do this:

client.index('myindex').deleteIfExists()
client.index('myindex').addDocuments(myDocuments)

TODO

• meilisearch-dart
• meilisearch-dotnet
• meilisearch-go
• meilisearch-java
• meilisearch-js
• meilisearch-php
• meilisearch-python (Adding delete if exists methods meilisearch-python#268)
• meilisearch-ruby
• meilisearch-rust
• meilisearch-swift

[curquiza]

Hello! Not sure to get it! Can you detail the context in which you would use this method?

[bidoubiwa]

for example on docs-scrapper. Before adding the new document you would typically delete the index before re-creating one add the settings and the documents. When updating databases I often go with the same solution, first delete if it existed, then add documents and settings.

[curquiza]

Oh you want to add the deleteIndexIfExist() to avoid doing the try/catch to check if the index already exists!

Ok, this would be a temporary solution because MeilISearch does not handle the swap index yet. We have to think if it's really worth taking time to add it to every SDK and then remove it before the release of the swap index.

[bidoubiwa]

This is something I used a lot in different databases:

POSTGRES/ MySQL/ most sql db's

deleting

DROP TABLE IF EXISTS mytable:

database delete

DROP DATABASE [IF EXISTS] database_name;

Mongo

returns false but not an error when attempting to delete a collection that exists.

Elasticsearch

Delete a document if it exist

{
"query": {
  "exists": {
    "field": "name"
  }
 }
}

and then remove it before the release of the swap index

Is this related to this issue https://github.com/meilisearch/transplant/issues/28 ?

[curquiza]

Is this related to this issue meilisearch/transplant#28 ?

Yes 🙂

[bidoubiwa]

The swap is great, but I think nonetheless user may still want that method for tests/security/shutdown. It would avoid that in our e2e tests we have to delete all indexes before running the tests (at least in javascript SDK).
It can be used in ateardown method or a onstart as it cleans the instance.

[bidoubiwa]

@curquiza @alallema the issue is waiting for a vote!

[curquiza]

The winner is:

client.index("myindex").deleteIfExist()
client.deleteIndexIfExists("myindex")

I pass it as ready to implement