bits28
The bits28 functions provide an API for working with "bit pattern" INT64
fields, as used in the clients_last_seen dataset
for desktop Firefox and similar datasets for other applications.
A powerful feature of the clients_last_seen methodology is that it doesn't
record specific metrics like MAU and WAU directly, but rather each row stores
a history of the discrete days on which a client was active in the past 28 days.
We could calculate active users in a 10 day or 25 day window just as efficiently
as a 7 day (WAU) or 28 day (MAU) window. But we can also define completely new
metrics based on these usage histories, such as various retention definitions.
The usage history is encoded as a "bit pattern" where the physical type of the field is a BigQuery INT64, but logically the integer represents an array of bits, with each 1 indicating a day where the given clients was active and each 0 indicating a day where the client was inactive.
active_in_range (UDF)
Return a boolean indicating if any bits are set in the specified range
of a bit pattern. The start_offset must be zero or a negative number
indicating an offset from the rightmost bit in the pattern. n_bits is
the number of bits to consider, counting right from the bit at
start_offset.
See detailed docs for the bits28 suite of functions: https://docs.telemetry.mozilla.org/cookbooks/clients_last_seen_bits.html#udf-reference
Parameters
INPUTS
bits INT64, start_offset INT64, n_bits INT64
OUTPUTS
BOOLEAN
days_since_seen (UDF)
Return the position of the rightmost set bit in an INT64 bit pattern.
To determine this position, we take a bitwise AND of the bit pattern and its complement, then we determine the position of the bit via base-2 logarithm; see https://stackoverflow.com/a/42747608/1260237
See detailed docs for the bits28 suite of functions: https://docs.telemetry.mozilla.org/cookbooks/clients_last_seen_bits.html#udf-reference
SELECT
mozfun.bits28.days_since_seen(18)
-- >> 1
Parameters
INPUTS
bits INT64
OUTPUTS
INT64
from_string (UDF)
Convert a string representing individual bits into an INT64.
Implementation based on https://stackoverflow.com/a/51600210/1260237
See detailed docs for the bits28 suite of functions: https://docs.telemetry.mozilla.org/cookbooks/clients_last_seen_bits.html#udf-reference
Parameters
INPUTS
s STRING
OUTPUTS
INT64
range (UDF)
Return an INT64 representing a range of bits from a source bit pattern.
The start_offset must be zero or a negative number indicating an offset from the rightmost bit in the pattern.
n_bits is the number of bits to consider, counting right from the bit at start_offset.
See detailed docs for the bits28 suite of functions: https://docs.telemetry.mozilla.org/cookbooks/clients_last_seen_bits.html#udf-reference
SELECT
-- Signature is bits28.range(offset_to_day_0, start_bit, number_of_bits)
mozfun.bits28.range(days_seen_bits, -13 + 0, 7) AS week_0_bits,
mozfun.bits28.range(days_seen_bits, -13 + 7, 7) AS week_1_bits
FROM
`mozdata.telemetry.clients_last_seen`
WHERE
submission_date > '2020-01-01'
Parameters
INPUTS
bits INT64, start_offset INT64, n_bits INT64
OUTPUTS
INT64
retention (UDF)
Return a nested struct providing booleans indicating whether a given client was active various time periods based on the passed bit pattern.
Parameters
INPUTS
bits INT64, submission_date DATE
to_dates (UDF)
Convert a bit pattern into an array of the dates is represents.
See detailed docs for the bits28 suite of functions: https://docs.telemetry.mozilla.org/cookbooks/clients_last_seen_bits.html#udf-reference
Parameters
INPUTS
bits INT64, submission_date DATE
OUTPUTS
ARRAY<DATE>
to_string (UDF)
Convert an INT64 field into a 28-character string representing the individual bits.
Implementation based on https://stackoverflow.com/a/51600210/1260237
See detailed docs for the bits28 suite of functions: https://docs.telemetry.mozilla.org/cookbooks/clients_last_seen_bits.html#udf-reference
SELECT
[mozfun.bits28.to_string(1), mozfun.bits28.to_string(2), mozfun.bits28.to_string(3)]
-- >>> ['0000000000000000000000000001',
-- '0000000000000000000000000010',
-- '0000000000000000000000000011']
Parameters
INPUTS
bits INT64
OUTPUTS
STRING