database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-09 22:41:56 +03:00
Code Activity

Make plpgsql use its DTYPE_REC code paths for composite-type variables.

Browse Source 
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
This commit is contained in:
Tom Lane
2018-02-13 18:52:21 -05:00
parent 2ac3e6acc2
commit 4b93f57999
20 changed files with 4596 additions and 913 deletions
Download Patch File Download Diff File Expand all files Collapse all files

84
src/backend/utils/cache/typcache.c vendored
View File

@ -259,12 +259,22 @@ static const dshash_parameters srtr_typmod_table_params = {
LWTRANCHE_SESSION_TYPMOD_TABLE
};
/* hashtable for recognizing registered record types */
static HTAB *RecordCacheHash = NULL;
/* arrays of info about registered record types, indexed by assigned typmod */
static TupleDesc *RecordCacheArray = NULL;
static int32 RecordCacheArrayLen = 0; /* allocated length of array */
static uint64 *RecordIdentifierArray = NULL;
static int32 RecordCacheArrayLen = 0; /* allocated length of above arrays */
static int32 NextRecordTypmod = 0; /* number of entries used */
/*
* Process-wide counter for generating unique tupledesc identifiers.
* Zero and one (INVALID_TUPLEDESC_IDENTIFIER) aren't allowed to be chosen
* as identifiers, so we start the counter at INVALID_TUPLEDESC_IDENTIFIER.
*/
static uint64 tupledesc_id_counter = INVALID_TUPLEDESC_IDENTIFIER;
static void load_typcache_tupdesc(TypeCacheEntry *typentry);
static void load_rangetype_info(TypeCacheEntry *typentry);
static void load_domaintype_info(TypeCacheEntry *typentry);
@ -793,10 +803,10 @@ load_typcache_tupdesc(TypeCacheEntry *typentry)
typentry->tupDesc->tdrefcount++;
/*
* In future, we could take some pains to not increment the seqno if the
* tupdesc didn't really change; but for now it's not worth it.
* In future, we could take some pains to not change tupDesc_identifier if
* the tupdesc didn't really change; but for now it's not worth it.
*/
typentry->tupDescSeqNo++;
typentry->tupDesc_identifier = ++tupledesc_id_counter;
relation_close(rel, AccessShareLock);
}
@ -1496,7 +1506,8 @@ cache_range_element_properties(TypeCacheEntry *typentry)
}
/*
* Make sure that RecordCacheArray is large enough to store 'typmod'.
* Make sure that RecordCacheArray and RecordIdentifierArray are large enough
* to store 'typmod'.
*/
static void
ensure_record_cache_typmod_slot_exists(int32 typmod)
@ -1505,6 +1516,8 @@ ensure_record_cache_typmod_slot_exists(int32 typmod)
{
RecordCacheArray = (TupleDesc *)
MemoryContextAllocZero(CacheMemoryContext, 64 * sizeof(TupleDesc));
RecordIdentifierArray = (uint64 *)
MemoryContextAllocZero(CacheMemoryContext, 64 * sizeof(uint64));
RecordCacheArrayLen = 64;
}
@ -1519,6 +1532,10 @@ ensure_record_cache_typmod_slot_exists(int32 typmod)
newlen * sizeof(TupleDesc));
memset(RecordCacheArray + RecordCacheArrayLen, 0,
(newlen - RecordCacheArrayLen) * sizeof(TupleDesc));
RecordIdentifierArray = (uint64 *) repalloc(RecordIdentifierArray,
newlen * sizeof(uint64));
memset(RecordIdentifierArray + RecordCacheArrayLen, 0,
(newlen - RecordCacheArrayLen) * sizeof(uint64));
RecordCacheArrayLen = newlen;
}
}
@ -1581,11 +1598,17 @@ lookup_rowtype_tupdesc_internal(Oid type_id, int32 typmod, bool noError)
/*
* Our local array can now point directly to the TupleDesc
* in shared memory.
* in shared memory, which is non-reference-counted.
*/
RecordCacheArray[typmod] = tupdesc;
Assert(tupdesc->tdrefcount == -1);
/*
* We don't share tupdesc identifiers across processes, so
* assign one locally.
*/
RecordIdentifierArray[typmod] = ++tupledesc_id_counter;
dshash_release_lock(CurrentSession->shared_typmod_table,
entry);
@ -1790,12 +1813,61 @@ assign_record_type_typmod(TupleDesc tupDesc)
RecordCacheArray[entDesc->tdtypmod] = entDesc;
recentry->tupdesc = entDesc;
/* Assign a unique tupdesc identifier, too. */
RecordIdentifierArray[entDesc->tdtypmod] = ++tupledesc_id_counter;
/* Update the caller's tuple descriptor. */
tupDesc->tdtypmod = entDesc->tdtypmod;
MemoryContextSwitchTo(oldcxt);
}
/*
* assign_record_type_identifier
*
* Get an identifier, which will be unique over the lifespan of this backend
* process, for the current tuple descriptor of the specified composite type.
* For named composite types, the value is guaranteed to change if the type's
* definition does. For registered RECORD types, the value will not change
* once assigned, since the registered type won't either. If an anonymous
* RECORD type is specified, we return a new identifier on each call.
*/
uint64
assign_record_type_identifier(Oid type_id, int32 typmod)
{
if (type_id != RECORDOID)
{
/*
* It's a named composite type, so use the regular typcache.
*/
TypeCacheEntry *typentry;
typentry = lookup_type_cache(type_id, TYPECACHE_TUPDESC);
if (typentry->tupDesc == NULL)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("type %s is not composite",
format_type_be(type_id))));
Assert(typentry->tupDesc_identifier != 0);
return typentry->tupDesc_identifier;
}
else
{
/*
* It's a transient record type, so look in our record-type table.
*/
if (typmod >= 0 && typmod < RecordCacheArrayLen &&
RecordCacheArray[typmod] != NULL)
{
Assert(RecordIdentifierArray[typmod] != 0);
return RecordIdentifierArray[typmod];
}
/* For anonymous or unrecognized record type, generate a new ID */
return ++tupledesc_id_counter;
}
}
/*
* Return the amout of shmem required to hold a SharedRecordTypmodRegistry.
* This exists only to avoid exposing private innards of