我想使用单个查询使用
Ruby散列或数组更新Postgres数据库中的许多记录,而不必遍历每个记录并调用单独的更新.
# {:id => :color}
my_hash = {
1 => 'red',
2 => 'blue',
3 => 'green'
}
我怎么不想这样做,因为它做了三个串行查询:
my_hash.each do |id, color|
MyModel.where(id: id).update_all(color: color)
end
我该怎么做呢:
MyModel.connection.execute <<-SQL
UPDATE my_models
SET color=something
FROM somehow_using(my_hash)
WHERE maybe_id=something
SQL
最佳答案 你可以使用案例:
update my_models
set color = case id
when 1 then 'red'
when 2 then 'blue'
when 3 then 'green'
end;
或将哈希保存在单独的表中:
create table my_hash (id int, color text);
insert into my_hash values
(1, 'red'),
(2, 'blue'),
(3, 'green');
update my_models m
set color = h.color
from my_hash h
where h.id = m.id;
还有一个选择,如果你知道选择哈希为jsonb的方法:
with hash as (
select '{"1": "red", "2": "blue", "3": "green"}'::jsonb h
)
update my_models
set color = value
from hash, jsonb_each_text(h)
where key::int = id;
OP ruby-fying klin的第三个选择:
sql = <<-SQL
with hash as (
select '#{my_hash.to_json}'::jsonb h
)
update my_models
set color = value
from hash, jsonb_each_text(h)
where key::int = id;
SQL
ActiveRecord::Base.connection.execute(sql)