HLL

HLL is used for approximate deduplication and performs better than Count Distinct when dealing with large data volumes. The load of HLL needs to be combined with functions like hll_hash. For more documentation, refer to HLL.

Usage Example

Step 1: Prepare Data

Create the following CSV file: test_hll.csv

1001|koga
1002|nijg
1003|lojn
1004|lofn
1005|jfin
1006|kon
1007|nhga
1008|nfubg
1009|huang
1010|buag

Step 2: Create Table in Database

CREATE TABLE testdb.test_hll(
    typ_id           BIGINT          NULL   COMMENT "ID",
    typ_name         VARCHAR(10)     NULL   COMMENT "NAME",
    pv               hll hll_union   NOT NULL   COMMENT "hll"
)
AGGREGATE KEY(typ_id,typ_name)
DISTRIBUTED BY HASH(typ_id) BUCKETS 10;

Step 3: Load Data

curl --location-trusted -u <doris_user>:<doris_password> \
    -H "column_separator:|" \
    -H "columns:typ_id,typ_name,pv=hll_hash(typ_id)" \
    -T test_hll.csv \
    -XPUT http://<fe_ip>:<fe_http_port>/api/testdb/test_hll/_stream_load

Step 4: Check Loaded Data

Use hll_cardinality to query:

mysql> select typ_id,typ_name,hll_cardinality(pv) from testdb.test_hll;
+--------+----------+---------------------+
| typ_id | typ_name | hll_cardinality(pv) |
+--------+----------+---------------------+
|   1010 | buag     |                   1 |
|   1002 | nijg     |                   1 |
|   1001 | koga     |                   1 |
|   1008 | nfubg    |                   1 |
|   1005 | jfin     |                   1 |
|   1009 | huang    |                   1 |
|   1004 | lofn     |                   1 |
|   1007 | nhga     |                   1 |
|   1003 | lojn     |                   1 |
|   1006 | kon      |                   1 |
+--------+----------+---------------------+
10 rows in set (0.06 sec)