PostgreSQL - INSERT an array of composite type containing arrays

问题

I have a composite type containing arrays of TEXT, etc. I am using this inside my main table to create an array of composite type.
How do I generate an INSERT command (without using the default field names of the composite type) ? Can I create a TEMPORARY TABLE with the array of composites and then insert it into the main table?

For example:

DROP TABLE collection;
DROP TABLE book_set;
DROP TYPE book;

CREATE TYPE book AS ( title TEXT, authors TEXT[], extra_spare TEXT );
CREATE TEMPORARY TABLE book_set ( books book[] );
CREATE TABLE shelf_collection ( shelf INT, position INT, books book[] );

-- Prefer to specify the fields I want, and NOT extra_spare as shown here!
-- AND it doesn't yet work... needs more casting?
INSERT INTO book_set( books ) VALUES (
      ( 'book1', array[ ( 'author1', 'author2' ) ], '' ),
      ( 'book2', array[ ( 'author3' )            ], '' ) ); 

-- And this obviously does not work yet!
INSERT INTO shelf_collection( shelf, position, books ) VALUES ( 1, 2, book_set ); 

The first INSERT fails with the message:

ERROR: INSERT has more expressions than target columns.

Fails same with or without array[] construct.

My real-world usage is significantly more complex, with the composite containing other composites, and many many fields.

I am not using multiple tables here for performance reasons (no join required to retrieve), and the inner composites and arrays are never referenced independently.

I am using perl(5.14.2) and DBI(1.616) and psql(9.1.7).

---

MORE INFO:

The following works, but how do I change it so that I do not need to specify ALL fields of book:

DROP TABLE shelf_collection;
DROP TYPE book;

CREATE TYPE  book AS          ( title TEXT, authors TEXT[], extra_spare TEXT );
CREATE TABLE shelf_collection ( shelf INT, position INT, books book[] );

INSERT INTO shelf_collection VALUES ( 12, 23, array[ROW( 'book title 1', array[ 'author1', 'author2' ], '' )::book] );

SELECT * FROM shelf_collection;

回答1:

PostgreSQL arrays are useful abstraction (non-standard, I should add), bit it can be easily abused - and I think this is exactly what you are trying to do.

You are trying to use arrays as an excuse and shortcut to NOT normalize your database schema. It may work with some kludges, but this is not worth it in the long run.

If you continue to use arrays, you will not be able to take advantage of many constructs which really make SQL useful. For example, you cannot effectively search your book_set table for any given author.

Right design would be to normalize - book_set should not contain array of authors. Instead, create separate table authors and separate link table book_author.

Granted, with normalized approach it is more awkward to insert data, and somewhat more awkward to query it - you will need to perform joins.

But, it makes possible to create almost any query imaginable. Also, with proper indexing it makes it work very fast even it your data set is extremely large.

来源：https://stackoverflow.com/questions/14225397/postgresql-insert-an-array-of-composite-type-containing-arrays