HASH

Calculates a hash value over the function arguments, producing a value in the range 0 <= x < 263.

The HASH function is typically used to segment a projection over a set of cluster nodes. The function selects a specific node for each row based on the values of the row columns. The HASH function distributes data evenly across the cluster, which facilitates optimal query execution.

Behavior type

Syntax

HASH ( { * | expression[,...] } )

Arguments

* | expression[,...]

One of the following:

• * (asterisk)

  Specifies to hash all columns in the queried table.

• expression

  An expression of any data type. Functions that are included in expression must be deterministic. If specified in a projection's hash segmentation clause, each expression typically resolves to a column reference.

Examples

=> SELECT HASH(product_price, product_cost) FROM product_dimension
     WHERE product_price = '11';
        hash
---------------------
 4157497907121511878
 1799398249227328285
 3250220637492749639
(3 rows)

See also