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nbtree index builds once stashed the "minimum key" for a page, which was used as the basis of the pivot tuple that gets placed in the next level up (i.e. the tuple that stores the downlink to the page in question). It doesn't quite work that way anymore, so the "minimum key" terminology now seems misleading (these days the minimum key is actually a straight copy of the high key from the left sibling, which is a distinct thing in subtle but important ways). Rename this concept to "low key". This name is a lot clearer given that there is now a sharp distinction between pivot and non-pivot tuples. Also remove comments that describe obsolete details about how the minimum key concept used to work. Rather than generating the minus infinity item for the leftmost page on a level by copying the new item and truncating that copy, simply allocate a small buffer. The old approach confusingly created the impression that the new item had some kind of significance. This was another artifact of how things used to work before commits 8224de4f and dd299df8.
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/.