sample.sql_in File Reference

SQL functions for random sampling. More...

Functions
bytea8	weighted_sample_transition_int64 (bytea8 state, bigint value, float8 weight)
bytea8	weighted_sample_merge_int64 (bytea8 state_left, bytea8 state_right)
bigint	weighted_sample_final_int64 (bytea8 state)
aggregate bytea8	weighted_sample (bigint value, float8 weight)
	Sample a single row according to weights. More...
bytea8	weighted_sample_transition_vector (bytea8 state, float8[] value, float8 weight)
bytea8	weighted_sample_merge_vector (bytea8 state_left, bytea8 state_right)
float8 []	weighted_sample_final_vector (bytea8 state)
aggregate bytea8	weighted_sample (float8[] value, float8 weight)
integer	poisson_random (float8 mean)
float8	gamma_random (float8 alpha)
integer	index_weighted_sample (float8[])

Detailed Description

See also

For an overview of random-sampling functions, see the module description Random Sampling.

Function Documentation

gamma_random()

float8 gamma_random

(

float8

alpha

)

index_weighted_sample()

integer index_weighted_sample

(

float8

[]

)

poisson_random()

integer poisson_random

(

float8

mean

)

weighted_sample() [1/2]

aggregate bytea8 weighted_sample	(	bigint	value,
		float8	weight
	)

Parameters

value	Value of row. Uniqueness is not enforced. If a value occurs multiple times, the probability of sampling this value is proportional to the sum of its weights.
weight	Weight for row. A negative value here is treated has zero weight.

Returns

identifier of the selected row. The probability of sampling any particular row (value, weight) is weight/SUM(weight).

weighted_sample() [2/2]

aggregate bytea8 weighted_sample	(	float8 []	value,
		float8	weight
	)

weighted_sample_final_int64()

bigint weighted_sample_final_int64

(

bytea8

state

)

weighted_sample_final_vector()

float8 [] weighted_sample_final_vector

(

bytea8

state

)

weighted_sample_merge_int64()

bytea8 weighted_sample_merge_int64	(	bytea8	state_left,
		bytea8	state_right
	)

weighted_sample_merge_vector()

bytea8 weighted_sample_merge_vector	(	bytea8	state_left,
		bytea8	state_right
	)

weighted_sample_transition_int64()

bytea8 weighted_sample_transition_int64	(	bytea8	state,
		bigint	value,
		float8	weight
	)

weighted_sample_transition_vector()

bytea8 weighted_sample_transition_vector	(	bytea8	state,
		float8 []	value,
		float8	weight
	)