Created
November 3, 2012 19:57
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| -- Say I have a very large table with a composite primary key with four parts, | |
| -- primary key = (A, B, C, D) where these are all integers. I would like to be | |
| -- able to select blocks of records of 10,000 in ORDER BY (A, B, C, D) primary | |
| -- key order. Given the last block where the final | |
| -- row had (A = a, B = b, C = c, D = d) a query for the next block is: | |
| SELECT * FROM BigTable | |
| WHERE | |
| A > a OR | |
| (A = a AND B > b) OR | |
| (A = a AND B = b AND C > c) OR | |
| (A = a AND B = b AND C = c AND D > d) | |
| ORDER BY (A, B, C, D) | |
| LIMIT 10000; | |
| -- This query does not seem to run very fast though, is there a better way? | |
| -- Ah, I guess this can be collapsed down to: | |
| SELECT * FROM BigTable | |
| WHERE | |
| A >= a AND B >= b AND C >= c AND D > d | |
| ORDER BY (A, B, C, D) | |
| LIMIT 10000; | |
| -- but the query planner was probably smart enough to do that. I'll have | |
| -- to check if it is still not efficient. |
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