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Previously, any attempt to request a 3.x protocol version other than 3.0 would lead to a hard connection failure, which made the minor protocol version really no different from the major protocol version and precluded gentle protocol version breaks. Instead, when the client requests a 3.x protocol version where x is greater than 0, send the new NegotiateProtocolVersion message to convey that we support only 3.0. This makes it possible to introduce new minor protocol versions without requiring a connection retry when the server is older. In addition, if the startup packet includes name/value pairs where the name starts with "_pq_.", assume that those are protocol options, not GUCs. Include those we don't support (i.e. all of them, at present) in the NegotiateProtocolVersion message so that the client knows they were not understood. This makes it possible for the client to request previously-unsupported features without bumping the protocol version at all; the client can tell from the server's response whether the option was understood. It will take some time before servers that support these new facilities become common in the wild; to speed things up and make things easier for a future 3.1 protocol version, back-patch to all supported releases. Robert Haas and Badrul Chowdhury Discussion: http://postgr.es/m/BN6PR21MB0772FFA0CBD298B76017744CD1730@BN6PR21MB0772.namprd21.prod.outlook.com Discussion: http://postgr.es/m/30788.1498672033@sss.pgh.pa.us |
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README
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/.