Created
August 10, 2018 08:34
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Fetch Tables and Columns of a Postrgres database in Elixir
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defmodule DBSchema do | |
@doc """ | |
link = DBSchema.connect | |
tables = DBSchema.get_tables(link) | |
columns = Enum.map(tables, fn(table) -> %{table: table.name, columns: DBSchema.get_columns(link, table)} end) | |
""" | |
def connect() do | |
{_, conn} = Postgrex.start_link( | |
hostname: "localhost", | |
username: "postgres", | |
port: "5432", | |
password: nil, | |
database: "" # Name of your database (important) | |
) | |
%{ | |
connection: conn, | |
server: "localhost", | |
port: "5432", | |
username: "postgres", | |
password: nil, | |
database_name: "", # Name of your database (important) | |
} | |
end | |
# pass in a database and then get the tables using the Postgrex query then turn the rows into a table | |
def get_tables(db) do | |
{_, result} = Postgrex.query(db.connection, "SELECT table_name FROM information_schema.tables WHERE table_schema = 'public';", []) | |
result.rows | |
|> List.flatten | |
|> Enum.map(fn(x) -> %{ database: db, name: x } end) | |
end | |
def get_columns(db, table) do | |
{_, result} = Postgrex.query(db.connection, " | |
SELECT DISTINCT | |
a.attname as column_name, | |
format_type(a.atttypid, a.atttypmod) as data_type, | |
coalesce(i.indisprimary,false) as primary_key, | |
f.references_table as foreign_table, | |
f.references_field as foreign_field, | |
a.attnum as num | |
FROM pg_attribute a | |
JOIN pg_class pgc ON pgc.oid = a.attrelid | |
left JOIN ( | |
SELECT | |
tc.table_name as table, | |
kcu.column_name as field, | |
ccu.table_name AS references_table, | |
ccu.column_name AS references_field | |
FROM information_schema.table_constraints tc | |
LEFT JOIN information_schema.key_column_usage kcu | |
ON tc.constraint_catalog = kcu.constraint_catalog | |
AND tc.constraint_schema = kcu.constraint_schema | |
AND tc.constraint_name = kcu.constraint_name | |
LEFT JOIN information_schema.referential_constraints rc | |
ON tc.constraint_catalog = rc.constraint_catalog | |
AND tc.constraint_schema = rc.constraint_schema | |
AND tc.constraint_name = rc.constraint_name | |
LEFT JOIN information_schema.constraint_column_usage ccu | |
ON rc.unique_constraint_catalog = ccu.constraint_catalog | |
AND rc.unique_constraint_schema = ccu.constraint_schema | |
AND rc.unique_constraint_name = ccu.constraint_name | |
WHERE lower(tc.constraint_type) in ('foreign key') | |
) as f on a.attname = f.field | |
LEFT JOIN pg_index i ON | |
(pgc.oid = i.indrelid AND i.indkey[0] = a.attnum) | |
WHERE a.attnum > 0 AND pgc.oid = a.attrelid | |
AND pg_table_is_visible(pgc.oid) | |
AND NOT a.attisdropped | |
AND pgc.relname = '#{table.name}' | |
ORDER BY a.attnum;", []) | |
result.rows | |
|> Enum.map(&to_column/1) | |
end | |
defp to_column(row) do | |
{_,name} = Enum.fetch(row, 0) | |
type = Enum.fetch(row, 1) |> get_type | |
{_, foreign_table} = Enum.fetch(row, 3) | |
{_, foreign_field} = Enum.fetch(row, 4) | |
{_, is_pk} = Enum.fetch(row, 2) | |
%{ | |
name: name, | |
type: type, | |
primary_key: is_pk, | |
foreign_table: foreign_table, | |
foreign_field: foreign_field | |
} | |
end | |
defp get_type({_,type}) do | |
type | |
end | |
defp get_type(_) do | |
end | |
end |
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