greenplumn pg_enum 源码
greenplumn pg_enum 代码
文件路径：/src/backend/catalog/pg_enum.c
/*-------------------------------------------------------------------------
*
* pg_enum.c
* routines to support manipulation of the pg_enum relation
*
* Copyright (c) 2006-2019, PostgreSQL Global Development Group
*
*
* IDENTIFICATION
* src/backend/catalog/pg_enum.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "access/xact.h"
#include "catalog/binary_upgrade.h"
#include "catalog/catalog.h"
#include "catalog/indexing.h"
#include "catalog/pg_enum.h"
#include "catalog/pg_type.h"
#include "cdb/cdbvars.h"
#include "storage/lmgr.h"
#include "miscadmin.h"
#include "nodes/value.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/fmgroids.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "utils/syscache.h"
#include "catalog/oid_dispatch.h"
/*
* Hash table of enum value OIDs created during the current transaction by
* AddEnumLabel. We disallow using these values until the transaction is
* committed; otherwise, they might get into indexes where we can't clean
* them up, and then if the transaction rolls back we have a broken index.
* (See comments for check_safe_enum_use() in enum.c.) Values created by
* EnumValuesCreate are *not* blacklisted; we assume those are created during
* CREATE TYPE, so they can't go away unless the enum type itself does.
*/
static HTAB *enum_blacklist = NULL;
static void RenumberEnumType(Relation pg_enum, HeapTuple *existing, int nelems);
static int sort_order_cmp(const void *p1, const void *p2);
/*
* EnumValuesCreate
* Create an entry in pg_enum for each of the supplied enum values.
*
* vals is a list of Value strings.
*/
void
EnumValuesCreate(Oid enumTypeOid, List *vals)
{
Relation pg_enum;
NameData enumlabel;
Oid *oids;
int elemno,
num_elems;
Datum values[Natts_pg_enum];
bool nulls[Natts_pg_enum];
ListCell *lc;
HeapTuple tup;
num_elems = list_length(vals);
/*
* We do not bother to check the list of values for duplicates --- if you
* have any, you'll get a less-than-friendly unique-index violation. It is
* probably not worth trying harder.
*/
pg_enum = table_open(EnumRelationId, RowExclusiveLock);
/*
* Allocate OIDs for the enum's members.
*
* While this method does not absolutely guarantee that we generate no
* duplicate OIDs (since we haven't entered each oid into the table before
* allocating the next), trouble could only occur if the OID counter wraps
* all the way around before we finish. Which seems unlikely.
*/
oids = (Oid *) palloc(num_elems * sizeof(Oid));
elemno = 0;
foreach(lc, vals)
{
/*
* We assign even-numbered OIDs to all the new enum labels. This
* tells the comparison functions the OIDs are in the correct sort
* order and can be compared directly.
*/
char *lab = strVal(lfirst(lc));
Oid new_oid;
do
{
/*
* In QE node, however, use the OIDs assigned by the master (they are delivered
* out-of-band, see oid_dispatch.c.
*/
if (Gp_role == GP_ROLE_EXECUTE)
{
new_oid = GetPreassignedOidForEnum(enumTypeOid, lab);
break;
}
new_oid = GetNewOidWithIndex(pg_enum, EnumOidIndexId,
Anum_pg_enum_oid);
} while (new_oid & 1);
oids[elemno] = new_oid;
if (Gp_role == GP_ROLE_DISPATCH)
RememberAssignedOidForEnum(enumTypeOid, lab, new_oid);
elemno++;
}
Assert(elemno == num_elems);
/* sort them, just in case OID counter wrapped from high to low */
qsort(oids, num_elems, sizeof(Oid), oid_cmp);
/* and make the entries */
memset(nulls, false, sizeof(nulls));
elemno = 0;
foreach(lc, vals)
{
char *lab = strVal(lfirst(lc));
/*
* labels are stored in a name field, for easier syscache lookup, so
* check the length to make sure it's within range.
*/
if (strlen(lab) > (NAMEDATALEN - 1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_NAME),
errmsg("invalid enum label \"%s\"", lab),
errdetail("Labels must be %d characters or less.",
NAMEDATALEN - 1)));
values[Anum_pg_enum_oid - 1] = ObjectIdGetDatum(oids[elemno]);
values[Anum_pg_enum_enumtypid - 1] = ObjectIdGetDatum(enumTypeOid);
values[Anum_pg_enum_enumsortorder - 1] = Float4GetDatum(elemno + 1);
namestrcpy(&enumlabel, lab);
values[Anum_pg_enum_enumlabel - 1] = NameGetDatum(&enumlabel);
tup = heap_form_tuple(RelationGetDescr(pg_enum), values, nulls);
CatalogTupleInsert(pg_enum, tup);
heap_freetuple(tup);
elemno++;
}
/* clean up */
pfree(oids);
table_close(pg_enum, RowExclusiveLock);
}
/*
* EnumValuesDelete
* Remove all the pg_enum entries for the specified enum type.
*/
void
EnumValuesDelete(Oid enumTypeOid)
{
Relation pg_enum;
ScanKeyData key[1];
SysScanDesc scan;
HeapTuple tup;
pg_enum = table_open(EnumRelationId, RowExclusiveLock);
ScanKeyInit(&key[0],
Anum_pg_enum_enumtypid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(enumTypeOid));
scan = systable_beginscan(pg_enum, EnumTypIdLabelIndexId, true,
NULL, 1, key);
while (HeapTupleIsValid(tup = systable_getnext(scan)))
{
CatalogTupleDelete(pg_enum, &tup->t_self);
}
systable_endscan(scan);
table_close(pg_enum, RowExclusiveLock);
}
/*
* Initialize the enum blacklist for this transaction.
*/
static void
init_enum_blacklist(void)
{
HASHCTL hash_ctl;
memset(&hash_ctl, 0, sizeof(hash_ctl));
hash_ctl.keysize = sizeof(Oid);
hash_ctl.entrysize = sizeof(Oid);
hash_ctl.hcxt = TopTransactionContext;
enum_blacklist = hash_create("Enum value blacklist",
32,
&hash_ctl,
HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
}
/*
* AddEnumLabel
* Add a new label to the enum set. By default it goes at
* the end, but the user can choose to place it before or
* after any existing set member.
*/
void
AddEnumLabel(Oid enumTypeOid,
const char *newVal,
const char *neighbor,
bool newValIsAfter,
bool skipIfExists)
{
Relation pg_enum;
Oid newOid;
Datum values[Natts_pg_enum];
bool nulls[Natts_pg_enum];
NameData enumlabel;
HeapTuple enum_tup;
float4 newelemorder;
HeapTuple *existing;
CatCList *list;
int nelems;
int i;
/* check length of new label is ok */
if (strlen(newVal) > (NAMEDATALEN - 1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_NAME),
errmsg("invalid enum label \"%s\"", newVal),
errdetail("Labels must be %d characters or less.",
NAMEDATALEN - 1)));
/*
* Acquire a lock on the enum type, which we won't release until commit.
* This ensures that two backends aren't concurrently modifying the same
* enum type. Without that, we couldn't be sure to get a consistent view
* of the enum members via the syscache. Note that this does not block
* other backends from inspecting the type; see comments for
* RenumberEnumType.
*/
LockDatabaseObject(TypeRelationId, enumTypeOid, 0, ExclusiveLock);
/*
* Check if label is already in use. The unique index on pg_enum would
* catch this anyway, but we prefer a friendlier error message, and
* besides we need a check to support IF NOT EXISTS.
*/
enum_tup = SearchSysCache2(ENUMTYPOIDNAME,
ObjectIdGetDatum(enumTypeOid),
CStringGetDatum(newVal));
if (HeapTupleIsValid(enum_tup))
{
ReleaseSysCache(enum_tup);
if (skipIfExists)
{
ereport(NOTICE,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("enum label \"%s\" already exists, skipping",
newVal)));
return;
}
else
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("enum label \"%s\" already exists",
newVal)));
}
pg_enum = table_open(EnumRelationId, RowExclusiveLock);
/* If we have to renumber the existing members, we restart from here */
restart:
/* Get the list of existing members of the enum */
list = SearchSysCacheList1(ENUMTYPOIDNAME,
ObjectIdGetDatum(enumTypeOid));
nelems = list->n_members;
/* Sort the existing members by enumsortorder */
existing = (HeapTuple *) palloc(nelems * sizeof(HeapTuple));
for (i = 0; i < nelems; i++)
existing[i] = &(list->members[i]->tuple);
qsort(existing, nelems, sizeof(HeapTuple), sort_order_cmp);
if (neighbor == NULL)
{
/*
* Put the new label at the end of the list. No change to existing
* tuples is required.
*/
if (nelems > 0)
{
Form_pg_enum en = (Form_pg_enum) GETSTRUCT(existing[nelems - 1]);
newelemorder = en->enumsortorder + 1;
}
else
newelemorder = 1;
}
else
{
/* BEFORE or AFTER was specified */
int nbr_index;
int other_nbr_index;
Form_pg_enum nbr_en;
Form_pg_enum other_nbr_en;
/* Locate the neighbor element */
for (nbr_index = 0; nbr_index < nelems; nbr_index++)
{
Form_pg_enum en = (Form_pg_enum) GETSTRUCT(existing[nbr_index]);
if (strcmp(NameStr(en->enumlabel), neighbor) == 0)
break;
}
if (nbr_index >= nelems)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("\"%s\" is not an existing enum label",
neighbor)));
nbr_en = (Form_pg_enum) GETSTRUCT(existing[nbr_index]);
/*
* Attempt to assign an appropriate enumsortorder value: one less than
* the smallest member, one more than the largest member, or halfway
* between two existing members.
*
* In the "halfway" case, because of the finite precision of float4,
* we might compute a value that's actually equal to one or the other
* of its neighbors. In that case we renumber the existing members
* and try again.
*/
if (newValIsAfter)
other_nbr_index = nbr_index + 1;
else
other_nbr_index = nbr_index - 1;
if (other_nbr_index < 0)
newelemorder = nbr_en->enumsortorder - 1;
else if (other_nbr_index >= nelems)
newelemorder = nbr_en->enumsortorder + 1;
else
{
/*
* The midpoint value computed here has to be rounded to float4
* precision, else our equality comparisons against the adjacent
* values are meaningless. The most portable way of forcing that
* to happen with non-C-standard-compliant compilers is to store
* it into a volatile variable.
*/
volatile float4 midpoint;
other_nbr_en = (Form_pg_enum) GETSTRUCT(existing[other_nbr_index]);
midpoint = (nbr_en->enumsortorder +
other_nbr_en->enumsortorder) / 2;
if (midpoint == nbr_en->enumsortorder ||
midpoint == other_nbr_en->enumsortorder)
{
RenumberEnumType(pg_enum, existing, nelems);
/* Clean up and start over */
pfree(existing);
ReleaseCatCacheList(list);
goto restart;
}
newelemorder = midpoint;
}
}
/* Get a new OID for the new label */
if (Gp_role == GP_ROLE_EXECUTE || IsBinaryUpgrade)
{
/*
* In QE, the dispatcher has already allocated the OID for us.
*/
newOid = GetPreassignedOidForEnum(enumTypeOid, newVal);
}
else
{
/*
* Normal case: we need to allocate a new Oid for the value.
*
* We want to give the new element an even-numbered Oid if it's safe,
* which is to say it compares correctly to all pre-existing even
* numbered Oids in the enum. Otherwise, we must give it an odd Oid.
*/
for (;;)
{
bool sorts_ok;
/* Get a new OID (different from all existing pg_enum tuples) */
newOid = GetNewOidWithIndex(pg_enum, EnumOidIndexId,
Anum_pg_enum_oid);
/*
* Detect whether it sorts correctly relative to existing
* even-numbered labels of the enum. We can ignore existing
* labels with odd Oids, since a comparison involving one of those
* will not take the fast path anyway.
*/
sorts_ok = true;
for (i = 0; i < nelems; i++)
{
HeapTuple exists_tup = existing[i];
Form_pg_enum exists_en = (Form_pg_enum) GETSTRUCT(exists_tup);
Oid exists_oid = exists_en->oid;
if (exists_oid & 1)
continue; /* ignore odd Oids */
if (exists_en->enumsortorder < newelemorder)
{
/* should sort before */
if (exists_oid >= newOid)
{
sorts_ok = false;
break;
}
}
else
{
/* should sort after */
if (exists_oid <= newOid)
{
sorts_ok = false;
break;
}
}
}
if (sorts_ok)
{
/* If it's even and sorts OK, we're done. */
if ((newOid & 1) == 0)
break;
/*
* If it's odd, and sorts OK, loop back to get another OID and
* try again. Probably, the next available even OID will sort
* correctly too, so it's worth trying.
*/
}
else
{
/*
* If it's odd, and does not sort correctly, we're done.
* (Probably, the next available even OID would sort
* incorrectly too, so no point in trying again.)
*/
if (newOid & 1)
break;
/*
* If it's even, and does not sort correctly, loop back to get
* another OID and try again. (We *must* reject this case.)
*/
}
}
if (Gp_role == GP_ROLE_DISPATCH)
RememberAssignedOidForEnum(enumTypeOid, newVal, newOid);
}
/* Done with info about existing members */
pfree(existing);
ReleaseCatCacheList(list);
/* Create the new pg_enum entry */
memset(nulls, false, sizeof(nulls));
values[Anum_pg_enum_oid - 1] = ObjectIdGetDatum(newOid);
values[Anum_pg_enum_enumtypid - 1] = ObjectIdGetDatum(enumTypeOid);
values[Anum_pg_enum_enumsortorder - 1] = Float4GetDatum(newelemorder);
namestrcpy(&enumlabel, newVal);
values[Anum_pg_enum_enumlabel - 1] = NameGetDatum(&enumlabel);
enum_tup = heap_form_tuple(RelationGetDescr(pg_enum), values, nulls);
CatalogTupleInsert(pg_enum, enum_tup);
heap_freetuple(enum_tup);
table_close(pg_enum, RowExclusiveLock);
/* Set up the blacklist hash if not already done in this transaction */
if (enum_blacklist == NULL)
init_enum_blacklist();
/* Add the new value to the blacklist */
(void) hash_search(enum_blacklist, &newOid, HASH_ENTER, NULL);
}
/*
* RenameEnumLabel
* Rename a label in an enum set.
*/
void
RenameEnumLabel(Oid enumTypeOid,
const char *oldVal,
const char *newVal)
{
Relation pg_enum;
HeapTuple enum_tup;
Form_pg_enum en;
CatCList *list;
int nelems;
HeapTuple old_tup;
bool found_new;
int i;
/* check length of new label is ok */
if (strlen(newVal) > (NAMEDATALEN - 1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_NAME),
errmsg("invalid enum label \"%s\"", newVal),
errdetail("Labels must be %d characters or less.",
NAMEDATALEN - 1)));
/*
* Acquire a lock on the enum type, which we won't release until commit.
* This ensures that two backends aren't concurrently modifying the same
* enum type. Since we are not changing the type's sort order, this is
* probably not really necessary, but there seems no reason not to take
* the lock to be sure.
*/
LockDatabaseObject(TypeRelationId, enumTypeOid, 0, ExclusiveLock);
pg_enum = table_open(EnumRelationId, RowExclusiveLock);
/* Get the list of existing members of the enum */
list = SearchSysCacheList1(ENUMTYPOIDNAME,
ObjectIdGetDatum(enumTypeOid));
nelems = list->n_members;
/*
* Locate the element to rename and check if the new label is already in
* use. (The unique index on pg_enum would catch that anyway, but we
* prefer a friendlier error message.)
*/
old_tup = NULL;
found_new = false;
for (i = 0; i < nelems; i++)
{
enum_tup = &(list->members[i]->tuple);
en = (Form_pg_enum) GETSTRUCT(enum_tup);
if (strcmp(NameStr(en->enumlabel), oldVal) == 0)
old_tup = enum_tup;
if (strcmp(NameStr(en->enumlabel), newVal) == 0)
found_new = true;
}
if (!old_tup)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("\"%s\" is not an existing enum label",
oldVal)));
if (found_new)
ereport(ERROR,
(errcode(ERRCODE_DUPLICATE_OBJECT),
errmsg("enum label \"%s\" already exists",
newVal)));
/* OK, make a writable copy of old tuple */
enum_tup = heap_copytuple(old_tup);
en = (Form_pg_enum) GETSTRUCT(enum_tup);
ReleaseCatCacheList(list);
/* Update the pg_enum entry */
namestrcpy(&en->enumlabel, newVal);
CatalogTupleUpdate(pg_enum, &enum_tup->t_self, enum_tup);
heap_freetuple(enum_tup);
table_close(pg_enum, RowExclusiveLock);
}
/*
* Test if the given enum value is on the blacklist
*/
bool
EnumBlacklisted(Oid enum_id)
{
bool found;
/* If we've made no blacklist table, all values are safe */
if (enum_blacklist == NULL)
return false;
/* Else, is it in the table? */
(void) hash_search(enum_blacklist, &enum_id, HASH_FIND, &found);
return found;
}
/*
* Clean up enum stuff after end of top-level transaction.
*/
void
AtEOXact_Enum(void)
{
/*
* Reset the blacklist table, as all our enum values are now committed.
* The memory will go away automatically when TopTransactionContext is
* freed; it's sufficient to clear our pointer.
*/
enum_blacklist = NULL;
}
/*
* RenumberEnumType
* Renumber existing enum elements to have sort positions 1..n.
*
* We avoid doing this unless absolutely necessary; in most installations
* it will never happen. The reason is that updating existing pg_enum
* entries creates hazards for other backends that are concurrently reading
* pg_enum. Although system catalog scans now use MVCC semantics, the
* syscache machinery might read different pg_enum entries under different
* snapshots, so some other backend might get confused about the proper
* ordering if a concurrent renumbering occurs.
*
* We therefore make the following choices:
*
* 1. Any code that is interested in the enumsortorder values MUST read
* all the relevant pg_enum entries with a single MVCC snapshot, or else
* acquire lock on the enum type to prevent concurrent execution of
* AddEnumLabel().
*
* 2. Code that is not examining enumsortorder can use a syscache
* (for example, enum_in and enum_out do so).
*/
static void
RenumberEnumType(Relation pg_enum, HeapTuple *existing, int nelems)
{
int i;
/*
* We should only need to increase existing elements' enumsortorders,
* never decrease them. Therefore, work from the end backwards, to avoid
* unwanted uniqueness violations.
*/
for (i = nelems - 1; i >= 0; i--)
{
HeapTuple newtup;
Form_pg_enum en;
float4 newsortorder;
newtup = heap_copytuple(existing[i]);
en = (Form_pg_enum) GETSTRUCT(newtup);
newsortorder = i + 1;
if (en->enumsortorder != newsortorder)
{
en->enumsortorder = newsortorder;
CatalogTupleUpdate(pg_enum, &newtup->t_self, newtup);
}
heap_freetuple(newtup);
}
/* Make the updates visible */
CommandCounterIncrement();
}
/* qsort comparison function for tuples by sort order */
static int
sort_order_cmp(const void *p1, const void *p2)
{
HeapTuple v1 = *((const HeapTuple *) p1);
HeapTuple v2 = *((const HeapTuple *) p2);
Form_pg_enum en1 = (Form_pg_enum) GETSTRUCT(v1);
Form_pg_enum en2 = (Form_pg_enum) GETSTRUCT(v2);
if (en1->enumsortorder < en2->enumsortorder)
return -1;
else if (en1->enumsortorder > en2->enumsortorder)
return 1;
else
return 0;
}
Size
EstimateEnumBlacklistSpace(void)
{
size_t entries;
if (enum_blacklist)
entries = hash_get_num_entries(enum_blacklist);
else
entries = 0;
/* Add one for the terminator. */
return sizeof(Oid) * (entries + 1);
}
void
SerializeEnumBlacklist(void *space, Size size)
{
Oid *serialized = (Oid *) space;
/*
* Make sure the hash table hasn't changed in size since the caller
* reserved the space.
*/
Assert(size == EstimateEnumBlacklistSpace());
/* Write out all the values from the hash table, if there is one. */
if (enum_blacklist)
{
HASH_SEQ_STATUS status;
Oid *value;
hash_seq_init(&status, enum_blacklist);
while ((value = (Oid *) hash_seq_search(&status)))
*serialized++ = *value;
}
/* Write out the terminator. */
*serialized = InvalidOid;
/*
* Make sure the amount of space we actually used matches what was
* estimated.
*/
Assert((char *) (serialized + 1) == ((char *) space) + size);
}
void
RestoreEnumBlacklist(void *space)
{
Oid *serialized = (Oid *) space;
Assert(!enum_blacklist);
/*
* As a special case, if the list is empty then don't even bother to
* create the hash table. This is the usual case, since enum alteration
* is expected to be rare.
*/
if (!OidIsValid(*serialized))
return;
/* Read all the values into a new hash table. */
init_enum_blacklist();
do
{
hash_search(enum_blacklist, serialized++, HASH_ENTER, NULL);
} while (OidIsValid(*serialized));
}
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