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Contents
# frozen_string_literal: true
module TableSaw
module Queries
class ForeignKeyRelationships
QUERY = <<~SQL
select
tc.constraint_name,
tc.table_name as from_table,
kcu.column_name as from_column,
ccu.table_name as to_table,
ccu.column_name as to_column
from information_schema.table_constraints tc
join information_schema.key_column_usage kcu on tc.constraint_name = kcu.constraint_name
join information_schema.constraint_column_usage ccu on tc.constraint_name = ccu.constraint_name
where tc.constraint_type = 'FOREIGN KEY'
SQL
def belongs_to
@belongs_to ||= result.each_with_object(Hash.new { |h, k| h[k] = {} }) do |row, memo|
memo[row['from_table']][row['from_column']] = row['to_table']
end
end
def has_many
@has_many ||= result.each_with_object(Hash.new { |h, k| h[k] = [] }) do |row, memo|
memo[row['to_table']].push([row['from_table'], row['from_column']])
end
end
def constraint_names
@constraint_names ||= result.each_with_object(Hash.new { |h, k| h[k] = [] }) do |row, memo|
memo[row['from_table']].push(row['constraint_name'])
end
end
private
def result
@result ||= TableSaw::Connection.exec(QUERY)
end
end
end
end
Version data entries
10 entries across 10 versions & 1 rubygems