• Andres Freund's avatar
    Remove WITH OIDS support, change oid catalog column visibility. · 578b2297
    Andres Freund authored
    Previously tables declared WITH OIDS, including a significant fraction
    of the catalog tables, stored the oid column not as a normal column,
    but as part of the tuple header.
    
    This special column was not shown by default, which was somewhat odd,
    as it's often (consider e.g. pg_class.oid) one of the more important
    parts of a row.  Neither pg_dump nor COPY included the contents of the
    oid column by default.
    
    The fact that the oid column was not an ordinary column necessitated a
    significant amount of special case code to support oid columns. That
    already was painful for the existing, but upcoming work aiming to make
    table storage pluggable, would have required expanding and duplicating
    that "specialness" significantly.
    
    WITH OIDS has been deprecated since 2005 (commit ff02d0a05280e0).
    Remove it.
    
    Removing includes:
    - CREATE TABLE and ALTER TABLE syntax for declaring the table to be
      WITH OIDS has been removed (WITH (oids[ = true]) will error out)
    - pg_dump does not support dumping tables declared WITH OIDS and will
      issue a warning when dumping one (and ignore the oid column).
    - restoring an pg_dump archive with pg_restore will warn when
      restoring a table with oid contents (and ignore the oid column)
    - COPY will refuse to load binary dump that includes oids.
    - pg_upgrade will error out when encountering tables declared WITH
      OIDS, they have to be altered to remove the oid column first.
    - Functionality to access the oid of the last inserted row (like
      plpgsql's RESULT_OID, spi's SPI_lastoid, ...) has been removed.
    
    The syntax for declaring a table WITHOUT OIDS (or WITH (oids = false)
    for CREATE TABLE) is still supported. While that requires a bit of
    support code, it seems unnecessary to break applications / dumps that
    do not use oids, and are explicit about not using them.
    
    The biggest user of WITH OID columns was postgres' catalog. This
    commit changes all 'magic' oid columns to be columns that are normally
    declared and stored. To reduce unnecessary query breakage all the
    newly added columns are still named 'oid', even if a table's column
    naming scheme would indicate 'reloid' or such.  This obviously
    requires adapting a lot code, mostly replacing oid access via
    HeapTupleGetOid() with access to the underlying Form_pg_*->oid column.
    
    The bootstrap process now assigns oids for all oid columns in
    genbki.pl that do not have an explicit value (starting at the largest
    oid previously used), only oids assigned later by oids will be above
    FirstBootstrapObjectId. As the oid column now is a normal column the
    special bootstrap syntax for oids has been removed.
    
    Oids are not automatically assigned during insertion anymore, all
    backend code explicitly assigns oids with GetNewOidWithIndex(). For
    the rare case that insertions into the catalog via SQL are called for
    the new pg_nextoid() function can be used (which only works on catalog
    tables).
    
    The fact that oid columns on system tables are now normal columns
    means that they will be included in the set of columns expanded
    by * (i.e. SELECT * FROM pg_class will now include the table's oid,
    previously it did not). It'd not technically be hard to hide oid
    column by default, but that'd mean confusing behavior would either
    have to be carried forward forever, or it'd cause breakage down the
    line.
    
    While it's not unlikely that further adjustments are needed, the
    scope/invasiveness of the patch makes it worthwhile to get merge this
    now. It's painful to maintain externally, too complicated to commit
    after the code code freeze, and a dependency of a number of other
    patches.
    
    Catversion bump, for obvious reasons.
    
    Author: Andres Freund, with contributions by John Naylor
    Discussion: https://postgr.es/m/20180930034810.ywp2c7awz7opzcfr@alap3.anarazel.de
    578b2297
alter.out 34.6 KB