Hi Robert Many thanks for your answers. 2011/7/19 Robert Haas <robertmhaas@xxxxxxxxx>: > Putting the elements in order wouldn't really help, would it? I mean, > you'd need some kind of an index inside the hstore... which there > isn't. Sorry for my inprecise question. In fact elements of a hstore are stored in order of (keylength,key) with the key comparison done bytewise (not locale-dependent). See e.g. function hstoreUniquePairs in http://doxygen.postgresql.org/ . This ordered property is being used by some hstore functions but not all - and I'm still wondering why. Yours, Stefan 2011/7/19 Robert Haas <robertmhaas@xxxxxxxxx>: > On Sun, Jun 19, 2011 at 2:59 PM, Stefan Keller <sfkeller@xxxxxxxxx> wrote: >> 1. Obviously the '@>' has to be used in order to let use the GiST index. >> Why is the '->' operator not supported by GiST ('->' is actually >> mentioned in all examples of the doc.)? > > Because it's not a comparison operator. > >> 2. Currently the hstore elements are stored in order as they are >> coming from the insert statement / constructor. >> Why are the elements not ordered i.e. why is the hstore not cached in >> all hstore functions (like hstore_fetchval etc.)? > > Putting the elements in order wouldn't really help, would it? I mean, > you'd need some kind of an index inside the hstore... which there > isn't. > >> 3. In the source code 'hstore_io.c' one finds the following enigmatic >> note: "... very large hstore values can't be output. this could be >> fixed, but many other data types probably have the same issue." >> What is the max. length of a hstore (i.e. the max. length of the sum >> of all elements in text representation)? > > I think that anything of half a gigabyte or more is at risk of falling > down there. But probably it's not smart to use such big hstores > anyway. > >> 4. Last, I don't fully understand the following note in the hstore >> doc. (http://www.postgresql.org/docs/current/interactive/hstore.html >> ): >>> Notice that the old names are reversed from the convention >>> formerly followed by the core geometric data types! >> >> Why names? Why not rather 'operators' or 'functions'? > > It's referring to the operator names. > >> What does this "reversed from the convention" mean concretely? > > That comment could be a little more clear, but I think what it's > saying is that hstore's old @ is like the core geometic types old ~, > and visca versa. > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company > -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
