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pingyu 2020-12-29 01:55:47 +08:00
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docs/en/sql-reference/functions/other-functions.md
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@ -182,6 +182,14 @@ If `NULL` is passed to the function as input, then it returns the `Nullable(Noth
Gets the size of the block.
In ClickHouse, queries are always run on blocks (sets of column parts). This function allows getting the size of the block that you called it for.
## byteSize(...) {#function-bytesize}
Get an estimate of uncompressed byte size of its arguments in memory.
E.g. for UInt32 argument it will return constant 4, for String argument - the string length + 9 (terminating zero + length).
The function can take multiple arguments. The typical application is byteSize(*).
Use case: Suppose you have a service that stores data for multiple clients in one table. Users will pay per data volume. So, you need to implement accounting of users data volume. The function will allow to calculate the data size on per-row basis.
## materialize(x) {#materializex}
Turns a constant into a full column containing just one value.