On 7/15/2014 3:54 PM, John R Pierce wrote:
On 7/15/2014 1:26 PM, Andy Colson wrote:
As I understand indexes, they are a key value pair, that contain a
value and a position. You lookup the value then use the position to
seek into the database to load the record.
indexes are stored as a B-tree. each terminal node has a block number
for the target record.
Do we, or could we, load all the the matching index records, then sort
them by position? (maybe not all, maybe large batches)
b-trees are inherently ordered. data records, however are not.
When loading from the database, if access was slightly more sequential
(vs very random), would it increase performance?
Said another way:
I think of table scanning as sequential, and fast. That would be
loading db record 1,2,3, etc.
database tables are unordered sets, there is no record 1,2,3.
Would it be faster to load db records "mostly sequential": 1,3,4,7,10
compared to randomly: 7,3,10,1,4
its unclear to me what you mean here.
Ah, yea, sorry, I don't really mean record #1, I mean hard drive seek to
address 1. (where address came from the index lookup)
Know what I mean?
-Andy
