Re: Patch for bug#42208

[Ann W. Harrison]

I wrote:
> 
> There is no need to store index entries if the index key doesn't
> change.  The index still points to the "master" version of the
> record, which may not have the key value for any particular entry -
> entries may represent older versions of the record and require
> walking the record chain to verify their values.
> 

Sorry, I had my head on backward.  You don't need to "verify"
the values, and the index key probably points to the newest
version of the record that has that particular key value.  To
get values for other fields, you do have to walk the chain
to find the right version for you.

Suppose you have two disagreeable connections bickering
over the key value for a record. One insists it should be 'A'
and the other insists it should be 'B'. They alternately
start transactions to make the record look the way they
want it.  In a Falcon index there will be two entries, 'A'
and 'B', both pointing to the same primary record.

In Maria, there would be many entries like this

    insertingTID  removingTID  value recLoc

         1            2          A     34
         2            3          B     67
         3            4          A    102
         4            5          B    136
         5            6          A    158

and so on.  But how likely is that?

Cheers,

Ann