Inserting an Array into Postgres Database from a Ruby File - ruby

Question

I'm trying to transfer all the information from my Ruby file into a Postgres database. I am able to transfer the information when I do not have an array column, so I am assuming the error message I am getting is because of the array column I am trying to add. The error message I am getting is:
in `exec_prepared': ERROR: missing dimension value (PG::InvalidTextRepresentation)
Here is the code I used to connect my Ruby file to my Postgres database:
require 'pg'
class Postgres
# Create the connection instance. Scraping is the name of the database I am adding this information to
def connect
#conn = PG.connect(:dbname => 'scraping')
end
# Create our venue table
def createVenueTable
#conn.exec("CREATE TABLE venues (venue_number varchar(15) UNIQUE,...,img_array varchar[]);")
end
...
def prepareInsertVenueStatement
#conn.prepare("insert_venue", "insert into venues(venue_number,...,img_array) values ($1,...,$24)")
end
# Add a venue with the prepared statement.
def addVenue(venue_number,...,img_array)
#conn.exec_prepared("insert_venue", [venue_number,...,img_array])
end
end
When I check my Postgres database, the img_array column is made, however, I am unable to populate it. Please help! Thank you.

Answer 1

I would suggest using serialization to handle this so that you are actually just writing a string rather than an actual array.
require 'pg'
require 'yaml'
class Postgres
# Create the connection instance. Scraping is the name of the database I am adding this information to
def connect
#conn = PG.connect(:dbname => 'scraping')
end
# Create our venue table
def createVenueTable
#changed img_array to a varchar(8000) for storing serialized Array
#conn.exec("CREATE TABLE venues (venue_number varchar(15) UNIQUE,...,img_array varchar(8000));")
end
...
def prepareInsertVenueStatement
#conn.prepare("insert_venue", "insert into venues(venue_number,...,img_array) values ($1,...,$24)")
end
# Add a venue with the prepared statement.
def addVenue(venue_number,...,img_array)
#conn.exec_prepared("insert_venue", [venue_number,...,serialized(img_array)])
end
#serialize the Object
def serialized(obj)
YAML.dump(obj)
end
#deserialize the Object
def deserialized(obj)
YAML.load(obj)
end
end
Abstracted Usage Example just to show serialization
a = [1,2,4,5]
serialized = YAML.dump(a)
#=> "---\n- 1\n- 2\n- 3\n- 4\n- 5\n"
YAML.load(serialized)
#=> [1,2,3,4,5]
#Also works on Hash Objects
h = {name: "Image", type: "jpeg", data:[1,2,3,4,5]}
serial = YAML.dump(h)
#=> "---\n:name: Image\n:type: jpeg\n:data:\n- 1\n- 2\n- 3\n- 4\n- 5\n"
YAML.load(serial)
#=> {:name=>"Image", :type=>"jpeg", :data=>[1, 2, 3, 4, 5]}
Hope this helps you out with handling this issue.
If you need to store more than 8000 characters you can switch to varchar(MAX) or text column definitions. I would recommend varchar(MAX) because the data will be stored as a standard varchar until it exceeds 8000 character at which point the db basically converts it to a text column under the hood.