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Presently, string keys are not well-supported for dshash tables. The dshash code always copies key_size bytes into new entries' keys, and dshash.h only provides compare and hash functions that forward to memcmp() and tag_hash(), both of which do not stop at the first NUL. This means that callers must pad string keys so that the data beyond the first NUL does not adversely affect the results of copying, comparing, and hashing the keys. To better support string keys in dshash tables, this commit does a couple things: * A new copy_function field is added to the dshash_parameters struct. This function pointer specifies how the key should be copied into new table entries. For example, we only want to copy up to the first NUL byte for string keys. A dshash_memcpy() helper function is provided and used for all existing in-tree dshash tables without string keys. * A set of helper functions for string keys are provided. These helper functions forward to strcmp(), strcpy(), and string_hash(), all of which ignore data beyond the first NUL. This commit also adjusts the DSM registry's dshash table to use the new helper functions for string keys. Reviewed-by: Andy Fan Discussion: https://postgr.es/m/20240119215941.GA1322079%40nathanxps13
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. Copyright and license information can be found in the file COPYRIGHT. General documentation about this version of PostgreSQL can be found at: https://www.postgresql.org/docs/devel/ In particular, information about building PostgreSQL from the source code can be found at: https://www.postgresql.org/docs/devel/installation.html The latest version of this software, and related software, may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.