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The existing convention in SP-GiST is that any pass-by-value datatype is stored in Datum representation, i.e. it's of width sizeof(Datum) even when typlen is less than that. This is okay, or at least it's too late to change it, for prefix datums and node-label datums in inner (upper) tuples. But it's problematic for leaf datums, because we'd prefer those to be stored in Postgres' standard on-disk representation so that we can easily extend leaf tuples to carry additional "included" columns. I believe, however, that we can get away with just up and changing that. This would be an unacceptable on-disk-format break, but there are two big mitigating factors: 1. It seems quite unlikely that there are any SP-GiST opclasses out there that use pass-by-value leaf datatypes. Certainly none of the ones in core do, nor has codesearch.debian.net heard of any. Given what SP-GiST is good for, it's hard to conceive of a use-case where the leaf-level values would be both small and fixed-width. (As an example, if you wanted to index text values with the leaf level being just a byte, then every text string would have to be represented with one level of inner tuple per preceding byte, which would be horrendously space-inefficient and slow to access. You always want to use as few inner-tuple levels as possible, leaving as much as possible in the leaf values.) 2. Even granting that you have such an index, this change only breaks things on big-endian machines. On little-endian, the high order bytes of the Datum format will now just appear to be alignment padding space. So, change the code to store pass-by-value leaf datums in their usual on-disk form. Inner-tuple datums are not touched. This is extracted from a larger patch that intends to add support for "included" columns. I'm committing it separately for visibility in our commit logs. Pavel Borisov and Tom Lane, reviewed by Andrey Borodin Discussion: https://postgr.es/m/CALT9ZEFi-vMp4faht9f9Junb1nO3NOSjhpxTmbm1UGLMsLqiEQ@mail.gmail.com
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/.