Need BOL clarification about indexes

[pandatime]

Hi,

The following explanations in quotes below are from microsoft.com. My question is, when it says:

"When a new index structure is created, disk space for both the old (source) and new (target) structures is required in their appropriate files and filegroups. The old structure is not deallocated until the index creation transaction commits.

So, when they say "old (source)" what are they talking about in the case where the index doesn't even exist yet???

(This sentence would make more sense if they are talking about an online rebuild operation)

So, are they talking about "temporary structures" created in the TEMPDB during the index creation? As in:

All other index DDL operations require additional temporary disk space to use during the operation, and permanent disk space to store the new index structure or structures.

Is that what they mean by "old (source)"? It's kind of confusing!

Thanks

Full article:

Index Operations That Require Additional Disk Space
--------------------------------------------------------------------------------

All other index DDL operations require additional temporary disk space to use during the operation, and permanent disk space to store the new index structure or structures. For more information about index structures, see Tables and Index Data Structures Architecture.

When a new index structure is created, disk space for both the old (source) and new (target) structures is required in their appropriate files and filegroups. The old structure is not deallocated until the index creation transaction commits.

The following index DDL operations create new index structures and require additional disk space:

•CREATE INDEX
•CREATE INDEX WITH DROP_EXISTING
•ALTER INDEX REBUILD
•ALTER TABLE ADD CONSTRAINT (PRIMARY KEY or UNIQUE)
•ALTER TABLE DROP CONSTRAINT (PRIMARY KEY or UNIQUE) when the constraint is based on a clustered index
•DROP INDEX MOVE TO (Applies only to clustered indexes.)

 

[mrdenny]

I believe that they are talking about when you use the DROP_EXISTING flag.

Denny
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