instance method `column_definitions`

Ruby on Rails 8.0.4

Since v5.2.8.1 Private

Available in: v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

column_definitions(table_name)

Returns the list of a table’s column names, data types, and default values.

The underlying query is roughly:

SELECT column.name, column.type, default.value, column.comment
  FROM column LEFT JOIN default
    ON column.table_id = default.table_id
   AND column.num = default.column_num
 WHERE column.table_id = get_table_id('table_name')
   AND column.num > 0
   AND NOT column.is_dropped
 ORDER BY column.num

If the table name is not prefixed with a schema, the database will take the first match from the schema search path.

Query implementation notes:

- format_type includes the column size constraint, e.g. varchar(50)
- ::regclass is a function that gives the id for a table name

Parameters

table_name req

Source

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 1034
        def column_definitions(table_name)
          query(<<~SQL, "SCHEMA")
              SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                     pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod,
                     c.collname, col_description(a.attrelid, a.attnum) AS comment,
                     #{supports_identity_columns? ? 'attidentity' : quote('')} AS identity,
                     #{supports_virtual_columns? ? 'attgenerated' : quote('')} as attgenerated
                FROM pg_attribute a
                LEFT JOIN pg_attrdef d ON a.attrelid = d.adrelid AND a.attnum = d.adnum
                LEFT JOIN pg_type t ON a.atttypid = t.oid
                LEFT JOIN pg_collation c ON a.attcollation = c.oid AND a.attcollation <> t.typcollation
               WHERE a.attrelid = #{quote(quote_table_name(table_name))}::regclass
                 AND a.attnum > 0 AND NOT a.attisdropped
               ORDER BY a.attnum
          SQL
        end

Defined in activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb line 1034 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::ConnectionAdapters::PostgreSQLAdapter

Signature

Parameters