2 Commits (c015ccb306ec81bca3023818c9cf0113cae25be1)

Author	SHA1	Message	Date
Tom Lane	2efc924180	Detoast plpgsql variables if they might live across a transaction boundary. ... Up to now, it's been safe for plpgsql to store TOAST pointers in its variables because the ActiveSnapshot for whatever query called the plpgsql function will surely protect such TOAST values from being vacuumed away, even if the owning table rows are committed dead. With the introduction of procedures, that assumption is no longer good in "non atomic" executions of plpgsql code. We adopt the slightly brute-force solution of detoasting all TOAST pointers at the time they are stored into variables, if we're in a non-atomic context, just in case the owning row goes away. Some care is needed to avoid long-term memory leaks, since plpgsql tends to run with CurrentMemoryContext pointing to its call-lifespan context, but we shouldn't assume that no memory is leaked by heap_tuple_fetch_attr. In plpgsql proper, we can do the detoasting work in the "eval_mcontext". Most of the code thrashing here is due to the need to add this capability to expandedrecord.c as well as plpgsql proper. In expandedrecord.c, we can't assume that the caller's context is short-lived, so make use of the short-term sub-context that was already invented for checking domain constraints. In view of this repurposing, it seems good to rename that variable and associated code from "domain_check_cxt" to "short_term_cxt". Peter Eisentraut and Tom Lane Discussion: https://postgr.es/m/5AC06865.9050005@anastigmatix.net	8 years ago
Tom Lane	4b93f57999	Make plpgsql use its DTYPE_REC code paths for composite-type variables. ... Formerly, DTYPE_REC was used only for variables declared as "record"; variables of named composite types used DTYPE_ROW, which is faster for some purposes but much less flexible. In particular, the ROW code paths are entirely incapable of dealing with DDL-caused changes to the number or data types of the columns of a row variable, once a particular plpgsql function has been parsed for the first time in a session. And, since the stored representation of a ROW isn't a tuple, there wasn't any easy way to deal with variables of domain-over-composite types, since the domain constraint checking code would expect the value to be checked to be a tuple. A lesser, but still real, annoyance is that ROW format cannot represent a true NULL composite value, only a row of per-field NULL values, which is not exactly the same thing. Hence, switch to using DTYPE_REC for all composite-typed variables, whether "record", named composite type, or domain over named composite type. DTYPE_ROW remains but is used only for its native purpose, to represent a fixed-at-compile-time list of variables, for instance the targets of an INTO clause. To accomplish this without taking significant performance losses, introduce infrastructure that allows storing composite-type variables as "expanded objects", similar to the "expanded array" infrastructure introduced in commit 1dc5ebc90. A composite variable's value is thereby kept (most of the time) in the form of separate Datums, so that field accesses and updates are not much more expensive than they were in the ROW format. This holds the line, more or less, on performance of variables of named composite types in field-access-intensive microbenchmarks, and makes variables declared "record" perform much better than before in similar tests. In addition, the logic involved with enforcing composite-domain constraints against updates of individual fields is in the expanded record infrastructure not plpgsql proper, so that it might be reusable for other purposes. In further support of this, introduce a typcache feature for assigning a unique-within-process identifier to each distinct tuple descriptor of interest; in particular, DDL alterations on composite types result in a new identifier for that type. This allows very cheap detection of the need to refresh tupdesc-dependent data. This improves on the "tupDescSeqNo" idea I had in commit 687f096ea: that assigned identifying sequence numbers to successive versions of individual composite types, but the numbers were not unique across different types, nor was there support for assigning numbers to registered record types. In passing, allow plpgsql functions to accept as well as return type "record". There was no good reason for the old restriction, and it was out of step with most of the other PLs. Tom Lane, reviewed by Pavel Stehule Discussion: https://postgr.es/m/8962.1514399547@sss.pgh.pa.us	8 years ago