postgres-github.git / summary / log / commit / refs

commit    20efbdffeb6418afa13d6c8457054735d11c7e3a
Author:   Richard Guo <rguo@postgresql.org>
Date:     Mon Apr 20 08:00:22 2026 +0000

    Clean up remove_rel_from_query() after self-join elimination commit
    
    The self-join elimination (SJE) commit grafted self-join removal onto
    remove_rel_from_query(), which was originally written for left-join
    removal only.  This resulted in several issues:
    
    - Comments throughout remove_rel_from_query() still assumed only
      left-join removal, making the code misleading.
    
    - ChangeVarNodesExtended was called on phv->phexpr with subst=-1
      during left-join removal, which is pointless and confusing since any
      surviving PHV shouldn't reference the removed rel.
    
    - phinfo->ph_lateral was adjusted for left-join removal, which is
      unnecessary since the removed relid cannot appear in ph_lateral for
      outer joins.
    
    - The comment about attr_needed reconstruction was in
      remove_rel_from_query(), but the actual rebuild is performed by the
      callers.
    
    - EquivalenceClass processing in remove_rel_from_query() is redundant
      for self-join removal, since the caller (remove_self_join_rel)
      already handles ECs via update_eclasses().
    
    - In remove_self_join_rel(), ChangeVarNodesExtended was called on
      root->processed_groupClause, which contains SortGroupClause nodes
      that have no Var nodes to rewrite.  The accompanying comment
      incorrectly mentioned "HAVING clause".
    
    This patch fixes all these issues, clarifying the separation between
    left-join removal and self-join elimination code paths within
    remove_rel_from_query().  The resulting code is also better structured
    for adding new types of join removal (such as inner-join removal) in
    the future.
    
    Author: Richard Guo <guofenglinux@gmail.com>
    Reviewed-by: Tender Wang <tndrwang@gmail.com>
    Reviewed-by: Andrei Lepikhov <lepihov@gmail.com>
    Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com>
    Discussion: https://postgr.es/m/CAMbWs48JC4OVqE=3gMB6se2WmRNNfMyFyYxm-09vgpm+Vwe8Hg@mail.gmail.com

[parent: 04f9ea372a20]