feat(snowflake): Add support for QueryGenerator#tableExistsQuery

[sfc-gh-dgadomski]

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• Have you added new tests to prevent regressions?
• Does yarn test or yarn test-DIALECT pass with this change (including linting)?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
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Description Of Change

This is an additional PR to merge fix from #14930 (already merged into v7) into v6 branch

Starting from version 6.20.0 a new method tableExistsQuery is introduced and used by the sequelizesync method. Unfortunately this method is implemented in all dialects except snowflake. This causes snowflake dialect basically unusable. This PR fixes the issue by adding the implementation of tableExistsQuery in snowlake dialect.

[WikiRik]

Thanks for working on this! I'm rerunning the docs job in the hope that it was just flaky

[WikiRik]

Nope, the docs are not flaky

2022-10-04T11:29:45.2598963Z parse: /home/runner/work/sequelize/sequelize/src/dialects/snowflake/query-generator.js
2022-10-04T11:29:45.2771163Z �[31mwarning: could not parse the following code. if you want to use ECMAScript proposals, see https://esdoc.org/manual/feature.html#ecmascript-proposal�[32m
2022-10-04T11:29:45.2772577Z /home/runner/work/sequelize/sequelize/src/dialects/snowflake/query-generator.js
2022-10-04T11:29:45.2773073Z 171|   }
2022-10-04T11:29:45.2773753Z 172| 
2022-10-04T11:29:45.2774175Z 173|   tableExistsQuery(table) {
2022-10-04T11:29:45.2774561Z 174|     const tableName = table.tableName ?? table;
2022-10-04T11:29:45.2774955Z 175|     const schema = table.schema;
2022-10-04T11:29:45.2775188Z 176| 

Can you look into this?

[ephys]

I don't think docs are ever flaky. esdoc has been left unmaintained for a long time and doesn't support newer syntax such as ??. Thankfully we've migrated to TypeDoc in v7

[sdepold]

Since we now all approved the pr 😂 should we merge it or is the mentioned ?? Operator a Blocker?

[ephys]

I was waiting on the CI to be done, then forgot :)

[github-actions]

🎉 This PR is included in version 6.24.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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