avoid DataLayer insert ancestors precheck

[altendky]

Purpose:

The expectation is that we will not trigger collisions usually so the except block won't be triggered and we'll save an sql query.

extracted from #15613

Current Behavior:

New Behavior:

Testing Notes:

[almogdepaz]

now we always write and we read if this is a known row
previously we used to always read and write only if its a new row

it looks to me like this change has performance tradeoffs, whats the average expected case ?

[altendky]

Yes, this change is intended to boost performance by reducing the number of queries. I can't say that a detailed analysis has been done but evidence so far is that we tend to insert new rows, not re-insert the exact same info, so cutting the query count in half (for this function) when doing that expected normal case is an improvement.

The check is just in case we end up inserting the same keys (SQLite checked) with different values in other columns. It is a double check for errors elsewhere, but I wanted to get the optimization in place without working through whether the double check was critical or important or slightly useful or.... We think this does that.

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