num_vals()

num_vals(sketch UddSketch) RETURNS DOUBLE PRECISION
num_vals(digest tdigest) RETURNS DOUBLE PRECISION

Get the number of values contained in a percentile estimate. This is provided in order to save space when both a count and a percentile estimate are required as part of continuous aggregates. You can simply compute a single percentile estimator and do not need to specify a separate count aggregate, just extract the num_vals from the percentile estimator.

Required arguments

NameTypeDescription
sketch / digestUddSketch or tdigestThe percentile estimator to extract the number of values from, usually from a percentile_agg() call.

Returns

ColumnTypeDescription
num_valsDOUBLE PRECISIONThe number of values in the percentile estimate

Sample usage

SELECT num_vals(percentile_agg(data))
FROM generate_series(0, 100) data;
num_vals
-----------
       101

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