![]() An example of an enum type might be the days of the week, or a set of status values for a piece of data. They are equivalent to the enum types supported in a number of programming languages. Function based constraints or domains provide the advantage of instant increase of the length constraint, and on the basis that decreasing a string length constraint is rare, depesz concludes that one of them is usually the best choice for a length limit. Enumerated (enum) types are data types that comprise a static, ordered set of values. It also takes a detailed look at alternate ways on constraining the length when needed. The article does detailed testing to show that the performance of inserts and selects for all 4 data types are similar. In a parameterized query issued from c code to PostgreSQL 10.14 via dotConnect 7.7.832. text – for me a winner – over (n) data types because it lacks their problems, and over varchar – because it has distinct name operator does not exist: timestamp without time zone.varchar(n) – it's problematic to change the limit in live environment (requires exclusive lock while altering table).Spaces, plus it is problematic to change the limit char(n) – takes too much space when dealing with values shorter than n (pads them to n), and can lead to subtle errors because of adding trailing.There is no difference, under the hood it's all varlena ( variable length array). Postgres itself only knows of the < and > containment operators.At the marked position an operator is expected, but your operator is either not defined or has other argumet types. The EXISTS operator is a boolean operator that tests for existence of rows in a subquery. PostgreSQL can understand this, but will try to search for unary prefix (and a postfix) operator, which are not exist by default (they can be created however, but the error message says, that's not the case) Edit: F.ex. SELECT r.zip, point (2,3) <> point (g.lat, g.lon) AS distance.The migration looks like following: class CreateHotels < ActiveRecord::Migration Introduction to PostgreSQL EXISTS operator. ![]() ActiveRecord does this automatically when you use an interpolated condition form. Heroku says: Make sure the operator is adequate for the data type. This is the foreign key in the hotel model: user_id :integer I know, sqlite is pretty forgiving, but PostgreSQL is not. : SELECT "hotels".* FROM "hotels" WHERE ("hotels".user_id = creates the error. You might need to add explicit type casts. HINT: No operator matches the given name and argument type(s). ![]() LINE 1: SELECT "hotels".* FROM "hotels" WHERE ("hotels".user_id = 1) This is from the heroku logs: ActionView::Template::Error (PGError: ERROR: operator does not exist: character varying = integer My Rails app works on my local machine, but after deploying to heroku it crashes:
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