Re: BUG #7763: "CREATE TABLE ... (LIKE ... INCLUDING INDEXES ...)" does not work with indexes on composite types - Mailing list pgsql-bugs

On 2012-12-20 22:50:54 +0100, Andres Freund wrote:
> On 2012-12-20 21:17:04 +0100, Andres Freund wrote:
> > On 2012-12-20 12:40:44 +0000, norbi@nix.hu wrote:
> > > The following bug has been logged on the website:
> > >
> > > Bug reference:      7763
> > > Logged by:          Norbert Buchmuller
> > > Email address:      norbi@nix.hu
> > > PostgreSQL version: 9.2.2
> > > Operating system:   Linux 2.6.32, i386, Debian GNU/Linux 6.0.5
> > > Description:
> > >
> > > There's a table that has a B-Tree index on a composite type expression. When
> > > attempting to create another table just like the first table and with the
> > > indexes also "copied" using the "CREATE TABLE ... (LIKE ... INCLUDING
> > > INDEXES ...)" statement, it throws an error (see below) and the table is not
> > > created.
> > >
> > > I believe it's a bug, from the documentation i assumed that it should create
> > > the table with a similar index, no matter that the index is on a composite
> > > type expression.
> > >
> > > postgres@vger:~$ cat
> > > create_table_like_including_indexes-and-index_on_composite_type.sql
> > > \set VERBOSITY verbose
> > > \set ECHO all
> > > SELECT version();
> > > CREATE TYPE type1 AS (x int, y int);
> > > CREATE TABLE table1 (a int, b int);
> > > CREATE INDEX index1 ON table1 ( ( (a, b)::type1 ) );
> > > CREATE TABLE table2 ( LIKE table1 INCLUDING INDEXES );
> > > \d table2
> > > postgres@vger:~$ dropdb test1; createdb test1 && psql --no-align --tuples -d
> > > test1 -f create_table_like_including_indexes-and-index_on_composite_type.sql
> > >
> > > SELECT version();
> > > PostgreSQL 9.2.2 on i686-pc-linux-gnu, compiled by gcc-4.4.real (Debian
> > > 4.4.5-8) 4.4.5, 32-bit
> > > CREATE TYPE type1 AS (x int, y int);
> > > CREATE TYPE
> > > CREATE TABLE table1 (a int, b int);
> > > CREATE TABLE
> > > CREATE INDEX index1 ON table1 ( ( (a, b)::type1 ) );
> > > CREATE INDEX
> > > CREATE TABLE table2 ( LIKE table1 INCLUDING INDEXES );
> > > psql:create_table_like_including_indexes-and-index_on_composite_type.sql:7:
> > > ERROR:  42P16: column "" has pseudo-type record
> > > LOCATION:  CheckAttributeType, heap.c:496
> > > \d table2
> > > Did not find any relation named "table2".
> >
> > Concretely that seems to be transformRowExpr's fault. It overwrites
> > row_typeid even though its marked as COERCE_EXPLICIT_CAST.
> >
> > Now the original problem seems to be that we are transforming an already
> > transformed expression. generateClonedIndexStmt gets the expression from
> > the old index via nodeToString, remaps some attnos, but thats about
> > it.
> > ISTM IndexElem grow a cooked_expr member.
>
> +should
>
> Ok, here are two patches:
> * Add a cooked_expr member to IndexElem and use it for transformed
>   expressions, including filling it directly in generateClonedIndexStmt.
>
> * Follow the pattern set by other routines in parse_expr.c and don't
>   transformRowExpr the same expression twice.
>
> While the first one fixes the above bug - and I think its the right
> approach not to analyze the expression twice, the second one seems like
> a good idea anyway because as transformExpr says:
>  *    1. At least one construct (BETWEEN/AND) puts the same nodes
>  *    into two branches of the parse tree; hence, some nodes
>  *    are transformed twice.
>  *    2. Another way it can happen is that coercion of an operator or
>  *    function argument to the required type (via coerce_type())
>  *    can apply transformExpr to an already-transformed subexpression.
>  *    An example here is "SELECT count(*) + 1.0 FROM table".
>
> There unfortunately is not sufficient padding in IndexElem to do that
> without changing its size. Not sure whether we consider that to be a big
> problem for the back branches, its nothing user code should do, but
> ...

So nobody has an idea that would avoid changing the sizeof(IndexElem)?
We could just apply patch 2 to fix the issue at hand, but I am pretty
sure transforming the whole expression twice can create other problems
than just this.

IndexStmt has some padding available at the end, we could add a bool
"precooked" there, but that seems to be rather ugly.

Greetings,

Andres
--
 Andres Freund                       http://www.2ndQuadrant.com/
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