In a columnstore index, up to 1,048,576 rows compressed as a unit, giving one column segment for each column. Rows not yet compressed sit in open delta rowgroups inside the deltastore.
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Terms in this definition
- Index
Speeds up queries that filter on certain columns by keeping those columns sorted, with pointers back to each row; the price is more storage and slower writes.
- Column segment
One column's compressed values inside a single columnstore rowgroup, along with minimum and maximum metadata so queries can skip, or eliminate, segments they don't need.
- Deltastore
Where a columnstore index keeps small batches and trickle inserts, as B-tree delta rowgroups, until a rowgroup fills up at 1,048,576 rows and the tuple-mover compresses it.
Related terms
- Tuple mover
A columnstore background task that takes a closed delta rowgroup, once it holds 1,048,576 rows, and compresses it into columnstore format.