How do I run a ruby function inside an ActiveRecord query?

up vote
0
down vote

favorite

City.all.sample{rand(1..3)} I want the random function to generate the sample count. This always returns one record.

asked yesterday

tambakoo

5510

@iGian couple of hundred times. Less than a thousand.
– tambakoo
yesterday

1

[1, 2, 3, 4, 5, 6, 7].sample(rand(1..3))
– iGian
yesterday

@iGian that was super simple! Thanks.
– tambakoo
yesterday

sample is not an active record query, though.
– Sergio Tulentsev
yesterday

1

@tambakoo: that it is, but you are not passing your logic to it. It runs unaltered. And then sample acts on the results. And in general, you can't "pass a ruby function to be used in a query". That's the whole point of the databases: to filter/sort/return data with maximum efficiency.
– Sergio Tulentsev
yesterday

|
show 1 more comment

up vote
0
down vote

favorite

City.all.sample{rand(1..3)} I want the random function to generate the sample count. This always returns one record.

asked yesterday

tambakoo

5510

@iGian couple of hundred times. Less than a thousand.
– tambakoo
yesterday

1

[1, 2, 3, 4, 5, 6, 7].sample(rand(1..3))
– iGian
yesterday

@iGian that was super simple! Thanks.
– tambakoo
yesterday

sample is not an active record query, though.
– Sergio Tulentsev
yesterday

1

@tambakoo: that it is, but you are not passing your logic to it. It runs unaltered. And then sample acts on the results. And in general, you can't "pass a ruby function to be used in a query". That's the whole point of the databases: to filter/sort/return data with maximum efficiency.
– Sergio Tulentsev
yesterday

|
show 1 more comment

up vote
0
down vote

favorite

City.all.sample{rand(1..3)} I want the random function to generate the sample count. This always returns one record.

asked yesterday

tambakoo

5510

City.all.sample{rand(1..3)} I want the random function to generate the sample count. This always returns one record.

ruby activerecord ruby-on-rails-5

asked yesterday

tambakoo

5510

asked yesterday

tambakoo

5510

asked yesterday

tambakoo

5510

asked yesterday

tambakoo

5510

asked yesterday

tambakoo

5510

@iGian couple of hundred times. Less than a thousand.
– tambakoo
yesterday

1

[1, 2, 3, 4, 5, 6, 7].sample(rand(1..3))
– iGian
yesterday

@iGian that was super simple! Thanks.
– tambakoo
yesterday

sample is not an active record query, though.
– Sergio Tulentsev
yesterday

1

@tambakoo: that it is, but you are not passing your logic to it. It runs unaltered. And then sample acts on the results. And in general, you can't "pass a ruby function to be used in a query". That's the whole point of the databases: to filter/sort/return data with maximum efficiency.
– Sergio Tulentsev
yesterday

|
show 1 more comment

@iGian couple of hundred times. Less than a thousand.
– tambakoo
yesterday

1

[1, 2, 3, 4, 5, 6, 7].sample(rand(1..3))
– iGian
yesterday

@iGian that was super simple! Thanks.
– tambakoo
yesterday

sample is not an active record query, though.
– Sergio Tulentsev
yesterday

1

@tambakoo: that it is, but you are not passing your logic to it. It runs unaltered. And then sample acts on the results. And in general, you can't "pass a ruby function to be used in a query". That's the whole point of the databases: to filter/sort/return data with maximum efficiency.
– Sergio Tulentsev
yesterday

@iGian couple of hundred times. Less than a thousand.
– tambakoo
yesterday

[1, 2, 3, 4, 5, 6, 7].sample(rand(1..3))
– iGian
yesterday

@iGian that was super simple! Thanks.
– tambakoo
yesterday

sample is not an active record query, though.
– Sergio Tulentsev
yesterday

@tambakoo: that it is, but you are not passing your logic to it. It runs unaltered. And then sample acts on the results. And in general, you can't "pass a ruby function to be used in a query". That's the whole point of the databases: to filter/sort/return data with maximum efficiency.
– Sergio Tulentsev
yesterday

|
show 1 more comment

1 Answer
1

active

oldest

votes

up vote
0
down vote

I'd suggest this way, to avoid retrieving all records:

n.times.map.with_object() { |_, a| a << City.find(City.ids.sample) }

It returns an array of records.

Of course, n can be a random integer.

answered yesterday

iGian

2,4442620

Why not City.order('RAND()').limit(rand(1..3))? (RAND(), RANDOM()) depending the DB.
– Sebastian Palma
yesterday

@SebastianPalma: terrible performance for larger tables.
– Sergio Tulentsev
yesterday

You could also City.find(City.ids.sample(n)) to reduce the number of queries and get a unique set of cities but you'd still be pull all the ids out of the cities table to do the sampling in Ruby and you'd still have an array. City.where(id: City.ids.sample(n)) would give you a relation but, again, you're still pulling all the ids out of the database.
– mu is too short
yesterday

add a comment |

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1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

up vote
0
down vote

I'd suggest this way, to avoid retrieving all records:

n.times.map.with_object() { |_, a| a << City.find(City.ids.sample) }

It returns an array of records.

Of course, n can be a random integer.

answered yesterday

iGian

2,4442620

Why not City.order('RAND()').limit(rand(1..3))? (RAND(), RANDOM()) depending the DB.
– Sebastian Palma
yesterday

@SebastianPalma: terrible performance for larger tables.
– Sergio Tulentsev
yesterday

You could also City.find(City.ids.sample(n)) to reduce the number of queries and get a unique set of cities but you'd still be pull all the ids out of the cities table to do the sampling in Ruby and you'd still have an array. City.where(id: City.ids.sample(n)) would give you a relation but, again, you're still pulling all the ids out of the database.
– mu is too short
yesterday

add a comment |

up vote
0
down vote

I'd suggest this way, to avoid retrieving all records:

n.times.map.with_object() { |_, a| a << City.find(City.ids.sample) }

It returns an array of records.

Of course, n can be a random integer.

answered yesterday

iGian

2,4442620

Why not City.order('RAND()').limit(rand(1..3))? (RAND(), RANDOM()) depending the DB.
– Sebastian Palma
yesterday

@SebastianPalma: terrible performance for larger tables.
– Sergio Tulentsev
yesterday

You could also City.find(City.ids.sample(n)) to reduce the number of queries and get a unique set of cities but you'd still be pull all the ids out of the cities table to do the sampling in Ruby and you'd still have an array. City.where(id: City.ids.sample(n)) would give you a relation but, again, you're still pulling all the ids out of the database.
– mu is too short
yesterday

add a comment |

up vote
0
down vote

I'd suggest this way, to avoid retrieving all records:

n.times.map.with_object() { |_, a| a << City.find(City.ids.sample) }

It returns an array of records.

Of course, n can be a random integer.

answered yesterday

iGian

2,4442620

I'd suggest this way, to avoid retrieving all records:

n.times.map.with_object() { |_, a| a << City.find(City.ids.sample) }

It returns an array of records.

Of course, n can be a random integer.

answered yesterday

iGian

2,4442620

answered yesterday

iGian

2,4442620

answered yesterday

iGian

2,4442620

answered yesterday

iGian

2,4442620

Why not City.order('RAND()').limit(rand(1..3))? (RAND(), RANDOM()) depending the DB.
– Sebastian Palma
yesterday

@SebastianPalma: terrible performance for larger tables.
– Sergio Tulentsev
yesterday

You could also City.find(City.ids.sample(n)) to reduce the number of queries and get a unique set of cities but you'd still be pull all the ids out of the cities table to do the sampling in Ruby and you'd still have an array. City.where(id: City.ids.sample(n)) would give you a relation but, again, you're still pulling all the ids out of the database.
– mu is too short
yesterday

add a comment |

Why not City.order('RAND()').limit(rand(1..3))? (RAND(), RANDOM()) depending the DB.
– Sebastian Palma
yesterday

@SebastianPalma: terrible performance for larger tables.
– Sergio Tulentsev
yesterday

You could also City.find(City.ids.sample(n)) to reduce the number of queries and get a unique set of cities but you'd still be pull all the ids out of the cities table to do the sampling in Ruby and you'd still have an array. City.where(id: City.ids.sample(n)) would give you a relation but, again, you're still pulling all the ids out of the database.
– mu is too short
yesterday

Why not City.order('RAND()').limit(rand(1..3))? (RAND(), RANDOM()) depending the DB.
– Sebastian Palma
yesterday

@SebastianPalma: terrible performance for larger tables.
– Sergio Tulentsev
yesterday

You could also City.find(City.ids.sample(n)) to reduce the number of queries and get a unique set of cities but you'd still be pull all the ids out of the cities table to do the sampling in Ruby and you'd still have an array. City.where(id: City.ids.sample(n)) would give you a relation but, again, you're still pulling all the ids out of the database.
– mu is too short
yesterday

add a comment |

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