ruby-on-rails - 将点数据列纬度和经度合并为一个纬度

Question

这是我当前从 CSV 导入的 rake 任务，我可以重写它以导入和删除前两列/使用空格作为分隔符将数据连接到一个 latlon 列吗？

require 'csv'

desc "Import public library data from csv file"

task :import => [:environment] do
  namespace :import_incidents_csv do
    task :create_incidents => :environment do
      ActiveRecord::Base.connection.execute "COPY PublicLibraryBranchLocations          (DistrictNumber, DistrictName, LibrarySystem, Type, Branch, Phone, Email, Website, PhysicalAddress, City, Province, PostalCode, Latitude, Longitude) FROM '/home/mgmacri/data/PublicLibraryBranchLocations.csv' DELIMITER ',' CSV;"
    end
  end
end

Answer 1

COPY 本身无法做到这一点，但您可以在导入之前更改 CSV。

一种方法是复制到一个临时表，然后使用类似这样的东西来导入：

INSERT INTO PublicLibraryBranchLocations(DistrictNumber, DistrictName, LibrarySystem, Type, Branch, Phone, Email, Website, PhysicalAddress, City, Province, PostalCode, LatLon) 
SELECT DistrictNumber, DistrictName, LibrarySystem, Type, Branch, Phone, Email, Website, PhysicalAddress, City, Province, PostalCode, Latitude ||' '|| Longitude
FROM TEMP_PublicLibraryBranchLocations;

如您所见， end 有一个串联Latitude ||' '|| Longitude。

另一种方法是使用file_fdw创建一个 FOREIGN TABLE ，因此您可以直接将 CSV 文件读取为一个表（可能称为PublicLibraryBranchLocations_FDW_CSV），而无需导入该表并将该表中的数据导入到PublicLibraryBranchLocations使用类似的东西：

INSERT INTO PublicLibraryBranchLocations(DistrictNumber, DistrictName, LibrarySystem, Type, Branch, Phone, Email, Website, PhysicalAddress, City, Province, PostalCode, LatLon) 
SELECT DistrictNumber, DistrictName, LibrarySystem, Type, Branch, Phone, Email, Website, PhysicalAddress, City, Province, PostalCode, Latitude ||' '|| Longitude
FROM PublicLibraryBranchLocations_FDW_CSV;