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From the MySQL Documentation The type of read varies for selects in clauses like INSERT INTO ... SELECT, UPDATE ... (SELECT), and CREATE TABLE ... SELECT that do not specify FOR UPDATE or LOCK IN SHARE MODE: By default, InnoDB uses stronger locks and the SELECT part acts like READ COMMITTED, where each consistent read, even within the same ...


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This is an answer assuming MySQL/InnoDB. Visibility rules are slightly different on Oracle: No, as you say, SET autocommit = 1 (default behavior) is that every single query is like if it has a START TRANSACTION; ... COMMIT; around it, committing after every query. That is different from READ UNCOMMITTED (which doesn't mean that there is not a lock). InnoDB ...


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Would a different kind of column be faster? For example an integer No. timestamp and timestamptz are just unsigned 64-bit integers internally anyway. Is there some way to not lock the column? It doesn't lock the column. It takes weak table lock that doesn't really block anything except DDL, and takes a row level lock on the row you're updating. ...


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If I run them serially, one right after the other, I'm expecting it will require 7 minutes to complete on average. Is this reasonable? If they use unrelated data sets, then yes. If they share a data set, and the cache is cold for the first query and the query is mostly I/O bound, then the second one might complete in moments. You need to consider ...



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