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1. =

描述：比较hll或hll_hashval的值是否相等。

返回值类型：bool

示例：

–hll

gbase=#

select (hll_empty() || hll_hash_integer(1)) = (hll_empty() || hll_hash_integer(1));

?column?

———-

t

(1 row)

–hll_hashval

gbase=# select hll_hash_integer(1) = hll_hash_integer(1);

?column?

———-

t

(1 row)

1. <> or !=

描述：比较hll或hll_hashval是否不相等。

返回值类型：bool

示例：

–hll

gbase=#

select (hll_empty() || hll_hash_integer(1)) <> (hll_empty() || hll_hash_integer(2));

?column?

———-

t

(1 row)

–hll_hashval

gbase=#

select hll_hash_integer(1) <> hll_hash_integer(2);

?column?

———-

t

(1 row)

1. ||

描述：可代表hll_add、hll_union、hll_add_rev三个函数的功能。

返回值类型：hll

示例：

–hll_add

gbase=#

select hll_empty() || hll_hash_integer(1);

?column?

—————————————————————————-

\x484c4c08000002002b0900000000000000f03f3e2921ff133fbaed3e2921ff133fbaed00

(1 row)

–hl_add_rev

gbase=#

select hll_hash_integer(1) || hll_empty();

?column?

—————————————————————————-

\x484c4c08000002002b0900000000000000f03f3e2921ff133fbaed3e2921ff133fbaed00

(1 row)

–hll_union

gbase=#

select (hll_empty() || hll_hash_integer(1)) || (hll_empty() || hll_hash_integer(2));

?column?

——————————————————————————————–

\x484c4c10002000002b090000000000000000400000000000000000b3ccc49320cca1ae3e2921ff133fbaed00

(1 row)

1. #

描述：计算出hll的Dintinct值, 同hll_cardinality函数。

返回值类型：int

示例：

gbase=#

select #(hll_empty() || hll_hash_integer(1));

?column?

———-

1

(1 row)