you can also stripe, eg:
c_1 starts at 1, skip=100
c_2 starts at 2, skip=100
c_$i starts at $i, skip=100 for 3..99
now you have 100x speed/parallelism. If single regionserver
assignment becomes a problem, use multiple tables.
On Sun, Feb 13, 2011 at 10:12 PM, Lars George lars.geo...@gmail.com wrote:
Hi SS,
Some people that do not need strict contiguous IDs also use block
increments of say 100. Each app server then gets 100 IDs to hand out
and in case it dies it gets its next assigned 100 IDs and leaves a
small gap behind. That way you can take the pressure of the counter if
that is going to be an issue for you. Depends on your insert frequency
obviously.
Lars
On Sun, Feb 13, 2011 at 7:10 PM, Something Something
mailinglist...@gmail.com wrote:
Hello,
Can you please tell me if this is the proper way of designing a table that's
got an auto increment key? If there's a better way please let me know that
as well.
After reading the mail archives, I learned that the best way is to use the
'incrementColumnValue' method of HTable.
So hypothetically speaking let's say I have to create a User - Orders
relationship. Every time user creates an order we will assign a system
generated (auto increment) id as primary key for the order.
I am thinking I could do this:
1) Create a table of Ids for various objects such as Order. It will have
just a single row with key 1 and column families for various objects.
When it's time to add a new order for a user I can do something like this:
HTable tableIds = new HTable(IDs);
Get get = new Get(Bytes.toBytes(1));
Result result = tableIds.get(get);
long newOrderId = tableIds.incrementColumnValue(result.getRow(), orders,
orderId, 1);
// In future I could use the same table for other objects as follows
// long newInvoiceId = tableIds.incrementColumnValue(result.getRow(),
invoices, invoiceId, 1);
2) Once the newOrderId is retrieved I can add the info about order to
UserOrder table with a key of format: userId + * + newOrderId. The
info family of this table will have columns such as orderAmount ,
orderDate etc.
As per the documentation, the 'incrementColumnValue' is done in exclusive
and serial fashion for each row with a rowlock. In other words, even in
multi-threading environment we are guaranteed to get a unique key per
thread, correct?
Is this a correct/good design for a table that needs auto increment key?
Please let me know. Thanks.
