Checking statements

Pg.verify db statements has Postgres describe every statement without running it, and compares the parameters and columns with what you declared. Run it in a test against a migrated database, and a renamed column fails the test instead of a request.

check.ml

module S = Rowtype
module Pg = Rowtype_postgres

let statements =
  [
    S.Any Orders.ship;
    S.Any Orders.count;
    S.Any Orders.find;
    S.Any Orders.of_customer;
    S.Any Orders.claim;
  ]

let check db = Pg.verify db statements

S.Any wraps a statement whatever it takes and answers, so every statement of a program goes in one list. Here they are the statements page’s Orders.

What it compares

For each statement, how many parameters and, for a statement that reads rows, how many columns, and each one’s type: an int an integer or an oid, a float a float, a text text, a name, a uuid or JSON, and the rest their own, a domain as the type it is made from. A parameter the database could not type is left to it. A statement it accepts is one Pg.run reads.

An enum is read and written by an S.enum each of whose labels is one of the enum’s. A label only the database has is no disagreement, since a migration adds one ahead of the code that reads it, and a row holding it is refused where it is read. An enum is also written from a text, and read as one through a cast, ::text.

Whether a column may be NULL is not checked: the database says so only of a column read as it is stored, and a query may promise more, so a check would refuse what is right. A NULL a shape does not allow fails where it is read, naming its column.

What it answers

`Disagreements names every problem, in words for a person, each naming its statement’s first line and where in it. A check that could not ask – a lost connection – is that failure, as a statement’s is, and no statement is said to disagree. Pg.error_to_string tells either.

On SQLite

Sq.verify db statements prepares every statement without running it and holds its parameters and columns to what you declared, a column of a table to its declared type: an integer column as one an int, an int64 or a bool reads, a real one as a float’s, a text one as text’s, an instant’s or any other kept as text, and a blob one as bytes or a uuid. A column made by an expression, or declared with no type, holds any kind of value, and is checked where it is read. Its placeholders are held to the rule a statement runs by, so a statement it passes is not refused for them when it runs.