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Tom Lane c7aba7c14e Support subscripting of arbitrary types, not only arrays. ... This patch generalizes the subscripting infrastructure so that any data type can be subscripted, if it provides a handler function to define what that means. Traditional variable-length (varlena) arrays all use array_subscript_handler(), while the existing fixed-length types that support subscripting use raw_array_subscript_handler(). It's expected that other types that want to use subscripting notation will define their own handlers. (This patch provides no such new features, though; it only lays the foundation for them.) To do this, move the parser's semantic processing of subscripts (including coercion to whatever data type is required) into a method callback supplied by the handler. On the execution side, replace the ExecEvalSubscriptingRef* layer of functions with direct calls to callback-supplied execution routines. (Thus, essentially no new run-time overhead should be caused by this patch. Indeed, there is room to remove some overhead by supplying specialized execution routines. This patch does a little bit in that line, but more could be done.) Additional work is required here and there to remove formerly hard-wired assumptions about the result type, collation, etc of a SubscriptingRef expression node; and to remove assumptions that the subscript values must be integers. One useful side-effect of this is that we now have a less squishy mechanism for identifying whether a data type is a "true" array: instead of wiring in weird rules about typlen, we can look to see if pg_type.typsubscript == F_ARRAY_SUBSCRIPT_HANDLER. For this to be bulletproof, we have to forbid user-defined types from using that handler directly; but there seems no good reason for them to do so. This patch also removes assumptions that the number of subscripts is limited to MAXDIM (6), or indeed has any hard-wired limit. That limit still applies to types handled by array_subscript_handler or raw_array_subscript_handler, but to discourage other dependencies on this constant, I've moved it from c.h to utils/array.h. Dmitry Dolgov, reviewed at various times by Tom Lane, Arthur Zakirov, Peter Eisentraut, Pavel Stehule Discussion: https://postgr.es/m/CA+q6zcVDuGBv=M0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w@mail.gmail.com Discussion: https://postgr.es/m/CA+q6zcVovR+XY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA@mail.gmail.com		5 years ago
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bitmapset.h	Move bitmap_hash and bitmap_match to bitmapset.c.	6 years ago
execnodes.h	Move per-agg and per-trans duplicate finding to the planner.	5 years ago
extensible.h	Update copyrights for 2020	6 years ago
lockoptions.h	Update copyrights for 2020	6 years ago
makefuncs.h	Improve our ability to regurgitate SQL-syntax function calls.	5 years ago
memnodes.h	Revert "Specialize MemoryContextMemAllocated()."	6 years ago
nodeFuncs.h	Suppress unnecessary RelabelType nodes in yet more cases.	5 years ago
nodes.h	Move per-agg and per-trans duplicate finding to the planner.	5 years ago
params.h	Initial pgindent and pgperltidy run for v13.	6 years ago
parsenodes.h	Remove operator_precedence_warning.	5 years ago
pathnodes.h	Fix missing outfuncs.c support for IncrementalSortPath.	5 years ago
pg_list.h	Add pg_nodiscard decorations to some functions	5 years ago
plannodes.h	Include result relation info in direct modify ForeignScan nodes.	5 years ago
primnodes.h	Support subscripting of arbitrary types, not only arrays.	5 years ago
print.h	Update copyrights for 2020	6 years ago
readfuncs.h	Update copyrights for 2020	6 years ago
replnodes.h	Update copyrights for 2020	6 years ago
subscripting.h	Support subscripting of arbitrary types, not only arrays.	5 years ago
supportnodes.h	Update copyrights for 2020	6 years ago
tidbitmap.h	Update copyrights for 2020	6 years ago
value.h	Update copyrights for 2020	6 years ago