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This commit splits the relation and index stats data, where the index data is now moved to a new kind called PGSTAT_KIND_INDEX. A benefit of this refactoring is a reduction of the shared memory required for each index, the new PgStat_StatIdxEntry including only the fields required for indexes. This leads to less data flushed to disk on shutdown. Another benefit is that the addition of new fields for relation-level stats is easier to think about. Note that indexes have no need for most of the xact-level fields that relations care about, clarifying the role of each counter for each relkind. System views are updated to use the index-level functions. Note this split means a possible break for tools that had the idea to call the SQL functions for relation stats (not documented), as now these would return 0 when queried for an index. These tools can use the new index functions to achieve the same result. As of this change, the pending statistics are still controlled by PgStat_TableStatus for both relation and index kinds. This is left as a follow-up piece, this one being good enough on its own. This commit is focused on the changes required for the SQL interface, shared memory management and the on-disk format. Bump catalog version. Bump PGSTAT_FILE_FORMAT_ID. Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com> Author: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/f572abe7-a1bb-e13b-48c7-2ca150546822@gmail.com