a65313f28b
Clarify the description of which transactions will block a CREATE INDEX CONCURRENTLY command from proceeding, and mention that the index might still not be usable after CREATE INDEX completes. (This happens if the index build detected broken HOT chains, so that pg_index.indcheckxmin gets set, and there are open old transactions preventing the xmin horizon from advancing past the index's initial creation. I didn't want to explain what broken HOT chains are, though, so I omitted an explanation of exactly when old transactions prevent the index from being used.) Per discussion with Chris Travers. Back-patch to all supported branches, since the same text appears in all of them.
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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.