What data store technology/solution allows very fast inserts, lookups and 'selects'

Here's my problem.

I want to ingest lots and lots of data .... right now millions and later billions of rows.

I have been using MySQL and I am playing around with PostgreSQL for now.

Inserting is easy, but before I insert I want to check if that particular records exists or not, if it does I don't want to insert. As the DB grows this operation (obviously) takes longer and longer.

If my data was in a Hashmap the look up would be o(1) so I thought I'd create a Hash index to help with lookups. But then I realised that if I have to compute the Hash again every time I will slow the process down massively (and if I don't compute the index I don't have o(1) lookup).

So I am in a quandry, is there a simple solution? Or a complex one? I am happy to try other datastores, however I need to be able to do reasonably compl开发者_如何学运维ex queries e.g. something to similar to SELECT statements with WHERE clauses, so I am not sure if no-sql solutions are applicable.

I am very much a novice, so I wouldn't be surprised if there is a trivial solution.

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Nosql Stores are good for handling huge inserts and updates

MongoDB has really good feature for update/Insert (called as upsert) based on whether the document is existing.

Check out this page from mongo doc

http://www.mongodb.org/display/DOCS/Updating#Updating-UpsertswithModifiers

Also you can checkout the safe mode in mongo connection. Which you can set it as false to get more efficiency in inserts.

http://www.mongodb.org/display/DOCS/Connections

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You could use CouchDB. Its no SQL so you can't do queries per se, but you can create design documents that allow you to run map/reduce functions on your data.