Mimimal Postgresql client for Jai

This module contains libpq bindings as well as some higher-level functions for…

• … connecting to a Postgresql database,
• … executing parameterized queries and
• … optionally parsing the results into a typed array.

It only supports synchronous execution for now.

Usage

First connect to a Postgresql instance using a connection uri string:

connection_str:="postgres://<username>:<password>@<host>:<port>/<db>";
conn, success:=connect(connection_str);
deferdisconnect(conn);

Then use conn to execute statements…

// Restrict schema accesssuccess=execute(conn, "SELECT pg_catalog.set_config('search_path', 'public', false)");

… or execute a query and automatically parse the result into an array of any given type:

query::#stringEND	SELECT * FROM tourist_attractions	WHERE city = $1 AND price < $2 AND min_age < $3	ORDER BY nameENDAttraction::struct {
name:string;
city:string;
price:string; // Numerics are parsed into stringsmin_age:int;
is_open:bool;
}
// Query parameters can be passed as variadic args after `query`:city:="Vienna";
price:=50;
min_age:=18;
attractions, success=execute(conn, Attraction, query, city, price, min_age);

By default, execute fails if the result contains a column that has no corresponding member in the struct type you passed. You can pass ignore_unknown = true to execute(…) to ignore unknown columns instead.

If your struct type contains members that aren’t present in the result (or are null), they will be left at their default values.

Memory model

You’re responsible for freeing everything (including strings) in the result array. Using a Pool allocator around your execute calls might be a good idea.

Supported query parameter types

• All integer types
• float and float64
• string
• bool

Supported return value column types

• INT2, INT4, INT8
• FLOAT4, FLOAT8
• NUMERIC (currently only parsed into string fields)
• BOOL
• CHAR, BPCHAR, VARCHAR, NAME, TEXT
• DATE, TIMESTAMP, TIMESTAMPTZ
• BYTEA
• OID
• UUID
• Custom enum types (CREATE TYPE … AS ENUM), which can be parsed into string or enum member fields.