Skip to content
DuckDB Extensions All extensions Apache DataSketches

CPC functions in the Apache DataSketches DuckDB extension

Function category

CPC

7 functions

[Compressed Probability Counting](https://datasketches.apache.org/docs/CPC/CpcSketches.html) — distinct-counting at roughly 40% the size of HLL at the same accuracy, traded against slower serialization. Choose this when you store many sketches at rest.

datasketch_cpc

Aggregate function CPC
Signature
datasketch_cpc(col0: INTEGER, col1: FLOAT | BLOB | DOUBLE | …) → sketch_cpc
Arguments (Positional)
Argument col0 Type INTEGER Mode Positional Description
Argument col1 Type FLOAT | BLOB | DOUBLE | …
12 concrete types
BIGINTBLOBDOUBLEFLOATINTEGERSMALLINTTINYINTUBIGINTUINTEGERUSMALLINTUTINYINTVARCHAR
Mode Positional Description
Description

Aggregate input values into a Compressed Probability Counting sketch — a distinct-count sketch that's roughly 40% smaller than HLL at the same accuracy, traded against slower serialization. Choose CPC when you store many sketches at rest and reads are infrequent. The leading lg_k controls the size/accuracy trade-off the same way it does for HLL.

1 Distinct-count with CPC 
SELECT datasketch_cpc_estimate(datasketch_cpc(12, user_id)) AS distinct_users
FROM events;
Related functions

datasketch_cpc_describe

Scalar function CPC
Signature
datasketch_cpc_describe(col0: sketch_cpc) → VARCHAR
Arguments (Positional)
Argument col0 Type sketch_cpc Mode Positional Description
Description

Return a string representation of the sketch

1 Example 1 
SELECT datasketch_cpc_describe(sketch);
Related functions

datasketch_cpc_estimate

Scalar function CPC
Signature
datasketch_cpc_estimate(col0: sketch_cpc) → DOUBLE
Arguments (Positional)
Argument col0 Type sketch_cpc Mode Positional Description
Description

Read the estimated distinct count from a CPC sketch.

1 Example 1 
SELECT datasketch_cpc_estimate(sketch);
Related functions

datasketch_cpc_is_empty

Scalar function CPC
Signature
datasketch_cpc_is_empty(col0: sketch_cpc) → BOOLEAN
Arguments (Positional)
Argument col0 Type sketch_cpc Mode Positional Description
Description

Return a boolean indicating if the sketch is empty

1 Example 1 
SELECT datasketch_cpc_is_empty(sketch);
Related functions

datasketch_cpc_lower_bound

Scalar function CPC
Signature
datasketch_cpc_lower_bound(col0: sketch_cpc, col1: UTINYINT) → DOUBLE
Arguments (Positional)
Argument col0 Type sketch_cpc Mode Positional Description
Argument col1 Type UTINYINT Mode Positional Description
Description

Return the lower bound of the number of distinct items seen by the sketch

1 Example 1 
SELECT datasketch_cpc_lower_bound(sketch, std_dev);
Related functions

datasketch_cpc_union

Aggregate function CPC
Signature
datasketch_cpc_union(col0: INTEGER, col1: sketch_cpc) → sketch_cpc
Arguments (Positional)
Argument col0 Type INTEGER Mode Positional Description
Argument col1 Type sketch_cpc Mode Positional Description
Description

Merge a column of sketch_cpc BLOBs into one rollup sketch — the standard per-partition / per-day rollup pattern.

1 Example 1 
SELECT datasketch_cpc_union(k, data);
Related functions

datasketch_cpc_upper_bound

Scalar function CPC
Signature
datasketch_cpc_upper_bound(col0: sketch_cpc, col1: UTINYINT) → DOUBLE
Arguments (Positional)
Argument col0 Type sketch_cpc Mode Positional Description
Argument col1 Type UTINYINT Mode Positional Description
Description

Return the upper bound of the number of distinct items seen by the sketch

1 Example 1 
SELECT datasketch_cpc_upper_bound(sketch, std_dev);
Related functions