Another issue regarding data migration from Magento 1.7.0.2 to Magento 2.3.5.

Question:
=========

* What are the conditions for products to display *'out of stock'* in Magento 2? I am clearly missing something!

Description:
------------

I see that all the configurable products now show ***'out of stock'*** when going to the product page on Magento 2. I am unable to figure out what conditions are used for displaying 'out of stock'. 

Basically, I want to ensure that the **configurable products** show their simple related products in the dropdown options (Magento default themes). The options are not currently shown because of this issue.

I tried the following:
----------------------

* Checked Tables `inventory_stock, inventory_stock_1, cataloginventory_stock_item, cataloginventory_stock_status, inventory_stock,cataloginventory_stock_status`.
* Only `cataloginventory_stock_status` has **qty of 0**.
* None of the tables that use `stock_status` are ever set to 0, everything is always 1.
* I even ran update quantity on `cataloginventory_stock_status`:

`UPDATE cataloginventory_stock_status SET qty = 999999 WHERE qty = 0;`

* Refreshing after clearing cache still showing *out of stock*, then immediately after reindexing `bin/magento indexer:reindex` I check `cataloginventory_stock_status` again, the **qty value is set back to 0**!

Also:
-----

* I noticed that the `cataloginventory_stock_status_idx` table is always **empty** even reindexing. Is this table even used?
* I have also tried to see the effect of **Manage Stock = 0**, but even then those products still show 'Out of Stock'.

I would really appreciate a solution where I can run MySQL queries (since this is a data migration) if possible.

Thanks!

### [Update - 2020/05/28]:

Does anybody have any advice regarding this please. 

* I have been unable to get migrated configurable products to work (still remains out of stock).
* *The issue*: I cannot just delete/reimport products - I need to eventually `bin/magento migrate:delta` so changing the ID sequences will break **delta migration** later on from the source database.

(The screenshots here are because of the comment below from @LitExtension Magento Migration). Only two configurable products are shown - one with 'simple', other with 'virtual' products, because they appear first in my SQL results.

*I do not know what is wrong.* Please see if there is anything I'm missing, or what else I need to supply information for.

**NOTE:** 
- *I do not have `is_in_stock` attribute mentioned.* The query returns no results. 

```
    SELECT * FROM eav_attribute ea 
    WHERE ea.attribute_code = 'is_in_stock';

```

### [Update Images]:

1. Image 1 - `catalog_product_entity`- *Filtered products 2x different configurables (one with simple products / other with virtual products)*

[![catalog_product_entity](https://i.stack.imgur.com/UB9ZW.jpg)](https://i.stack.imgur.com/UB9ZW.jpg)

2. Image 2 - `inventory_source_item` - same SKUs and their `status`.

[![inventory_source_item](https://i.stack.imgur.com/L9dFJ.jpg)](https://i.stack.imgur.com/L9dFJ.jpg)

3. Image 3 - `inventory_stock_1` - This is a **View**, so I assume as you mentioned when `reindex` happens `cataloginventory_stock_status` gets impacted, so the view data return `quantity = 0`.

[![inventory_stock_1](https://i.stack.imgur.com/kOl6w.jpg)](https://i.stack.imgur.com/kOl6w.jpg)

4. Image 4 - Joined data for `attribute = 'status'`

[![joined_cataloginventory_stock_status](https://i.stack.imgur.com/D5iH4.jpg)](https://i.stack.imgur.com/D5iH4.jpg)