Help Center/ GaussDB(DWS)/ SQL Syntax Reference (8.1.3.x)/ Functions and Operators/ HLL Functions and Operators/ HLL Operators
Updated on 2024-09-30 GMT+08:00
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HLL Operators

=

Description: Compares the values of hll and hll_hashval types to check whether they are the same.

Return type: bool

Example:

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--hll
SELECT (hll_empty() || hll_hash_integer(1)) = (hll_empty() || hll_hash_integer(1));
column 
----------
 t
(1 row)

--hll_hashval
SELECT hll_hash_integer(1) = hll_hash_integer(1);
 ?column? 
----------
 t
(1 row)

<> or !=

Description: Compares the values of hll and hll_hashval types to check whether they are different.

Return type: bool

Example:

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--hll
SELECT (hll_empty() || hll_hash_integer(1)) <> (hll_empty() || hll_hash_integer(2));
 ?column? 
----------
 t
(1 row)

--hll_hashval
SELECT hll_hash_integer(1) <> hll_hash_integer(2);
 ?column? 
----------
 t
(1 row)

||

Description: Represents the functions of hll_add, hll_union, and hll_add_rev.

Return type: hll

Example:

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--hll_add
SELECT hll_empty() || hll_hash_integer(1);
         ?column?         
--------------------------
 \x128b7f8895a3f5af28cafe
(1 row)
 
--hll_add_rev
SELECT hll_hash_integer(1) || hll_empty();
         ?column?         
--------------------------
 \x128b7f8895a3f5af28cafe
(1 row)
 
--hll_union
SELECT (hll_empty() || hll_hash_integer(1)) || (hll_empty() || hll_hash_integer(2));
                 ?column?                 
------------------------------------------
 \x128b7f8895a3f5af28cafeda0ce907e4355b60
(1 row)

#

Description: Calculates the number of distinct values of an HLL. It works the same as the hll_cardinality function.

Return type: integer

Example:

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SELECT #(hll_empty() || hll_hash_integer(1));
 ?column? 
----------
        1
(1 row)