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Document that list append/prepend are not idempotent and should be used with care

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Sylvain Lebresne 2012-11-23 15:36:34 +01:00
parent 6fb7512400
commit 64bc3354d3
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doc/cql3/CQL.textile
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@ -829,6 +829,8 @@ bc(sample).
UPDATE plays SET players = 5, scores = scores + [ 14, 21 ] WHERE id = '123-afde';
UPDATE plays SET players = 5, scores = [ 12 ] + scores WHERE id = '123-afde';
It should be noted that append and prepend are not idempotent operations. This means that if during an append or a prepend the operation timeout, it is not always safe to retry the operation (as this could result in the record appended or prepended twice).
Lists also provides the following operation: setting an element by its position in the list, removing an element by its position in the list and remove all the occurrence of a given value in the list. _However, and contrarily to all the other collection operations, these three operations induce an internal read before the update, and will thus typically have slower performance characteristics_. Those operations have the following syntax:
bc(sample).