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Tom Lane 042c9091f0 Produce more-optimal plans for bitmap scans on boolean columns.
The planner simplifies boolean comparisons such as "x = true" and
"x = false" down to "x" and "NOT x" respectively, to have a canonical
form to ease comparisons.  However, if we want to use an index on x,
the index AM APIs require us to reconstitute the comparison-operator
form of the indexqual.  While that works, in bitmap indexscans the
canonical form of the qual was emitted as a "filter" condition
although it really only needs to be a "recheck" condition, because
create_bitmap_scan_plan didn't recognize the equivalence of that
form with the generated indexqual.  booleq() is pretty cheap so that
likely doesn't make very much difference, but it's unsightly so
let's clean it up.

To fix, add a case to predicate_implied_by() to recognize the
equivalence of such clauses.  This is a relatively low-cost place to
add a check, and perhaps it will have additional use cases in future.

Richard Guo and Tom Lane, per discussion of bug #17618 from Sindy
Senorita.

Discussion: https://postgr.es/m/17618-7a2240bfaa7e84ae@postgresql.org
2022-11-08 10:36:04 -05:00
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doc Doc: Improve the description of confirmed_flush_lsn in pg_replication_slots. 2022-11-04 09:00:46 +05:30
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PostgreSQL Database Management System
=====================================

This directory contains the source code distribution of the PostgreSQL
database management system.

PostgreSQL is an advanced object-relational database management system
that supports an extended subset of the SQL standard, including
transactions, foreign keys, subqueries, triggers, user-defined types
and functions.  This distribution also contains C language bindings.

PostgreSQL has many language interfaces, many of which are listed here:

	https://www.postgresql.org/download/

See the file INSTALL for instructions on how to build and install
PostgreSQL.  That file also lists supported operating systems and
hardware platforms and contains information regarding any other
software packages that are required to build or run the PostgreSQL
system.  Copyright and license information can be found in the
file COPYRIGHT.  A comprehensive documentation set is included in this
distribution; it can be read as described in the installation
instructions.

The latest version of this software may be obtained at
https://www.postgresql.org/download/.  For more information look at our
web site located at https://www.postgresql.org/.