Aggregate Functions

For more information, see Aggregate Streaming Data With ksqlDB.

AVG

AVG(col1)

Stream, Table

Return the average value for a given column.

COLLECT_LIST

COLLECT_LIST(col1)

Stream, Table

Return an array containing all the values of col1 from each input row (for the specified grouping and time window, if any). Currently only works for simple types (not Map, Array, or Struct). This version limits the size of the result Array to a maximum of 1000 entries and any values beyond this limit are silently ignored. When using with a window type of session, it can sometimes happen that two session windows get merged together into one when a late-arriving record with a timestamp between the two windows is processed. In this case the 1000 record limit is calculated by first considering all the records from the first window, then the late-arriving record, then the records from the second window in the order they were originally processed.

COLLECT_SET

COLLECT_SET(col1)

Stream

Return an array containing the distinct values of col1 from each input row (for the specified grouping and time window, if any). Currently only works for simple types (not Map, Array, or Struct). This version limits the size of the result Array to a maximum of 1000 entries and any values beyond this limit are silently ignored. When using with a window type of session, it can sometimes happen that two session windows get merged together into one when a late-arriving record with a timestamp between the two windows is processed. In this case the 1000 record limit is calculated by first considering all the records from the first window, then the late-arriving record, then the records from the second window in the order they were originally processed.

COUNT

COUNT(col1), COUNT(*)

Stream, Table

Count the number of rows. When col1 is specified, the count returned will be the number of rows where col1 is non-null. When * is specified, the count returned will be the total number of rows.

COUNT_DISTINCT

COUNT_DISTINCT(col1)

Stream, Table

Returns the approximate number of unique values of col1 in a group. The function implementation uses HyperLogLog to estimate cardinalties of 10^9 with a typical standard error of 2%.

HISTOGRAM

HISTOGRAM(col1)

Stream, Table

Return a map containing the distinct String values of col1 mapped to the number of times each one occurs for the given window. This version limits the number of distinct values which can be counted to 1000, beyond which any additional entries are ignored. When using with a window type of session, it can sometimes happen that two session windows get merged together into one when a late-arriving record with a timestamp between the two windows is processed. In this case the 1000 record limit is calculated by first considering all the records from the first window, then the late-arriving record, then the records from the second window in the order they were originally processed.

MAX

MAX(col1)

Stream

Return the maximum value for a given column and window. Note: rows where col1 is null will be ignored.

MIN

MIN(col1)

Stream

Return the minimum value for a given column and window. Note: rows where col1 is null will be ignored.

SUM

SUM(col1)

Stream, Table

Sums the column values. Note: rows where col1 is null will be ignored.

TOPK

TOPK(col1, k)

Stream

Return the Top K values for the given column and window Note: rows where col1 is null will be ignored.

TOPKDISTINCT

TOPKDISTINCT(col1, k)

Stream

Return the distinct Top K values for the given column and window Note: rows where col1 is null will be ignored.

Page last revised on: 2020-02-07


Last update: 2020-02-07