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Editorial review of SET UNLOGGED

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Add a succint comment explaining why it's correct to change the
persistence in this way.  Also s/loggedness/persistence/ because native
speakers didn't like the latter term.

Fabrízio and Álvaro
This commit is contained in:
Alvaro Herrera 2014-08-25 13:50:19 -04:00
parent 9ee16b49f0
commit 7636c0c821
1 changed files with 21 additions and 14 deletions
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35
src/backend/commands/tablecmds.c
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@ -152,7 +152,7 @@ typedef struct AlteredTableInfo
bool new_notnull; /* T if we added new NOT NULL constraints */
bool rewrite; /* T if a rewrite is forced */
Oid newTableSpace; /* new tablespace; 0 means no change */
bool chgLoggedness; /* T if SET LOGGED/UNLOGGED is used */
bool chgPersistence; /* T if SET LOGGED/UNLOGGED is used */
char newrelpersistence; /* if above is true */
/* Objects to rebuild after completing ALTER TYPE operations */
List *changedConstraintOids; /* OIDs of constraints to rebuild */
@ -388,8 +388,8 @@ static void change_owner_recurse_to_sequences(Oid relationOid,
static void ATExecClusterOn(Relation rel, const char *indexName,
LOCKMODE lockmode);
static void ATExecDropCluster(Relation rel, LOCKMODE lockmode);
static bool ATPrepChangeLoggedness(Relation rel, bool toLogged);
static void ATChangeIndexesLoggedness(Oid relid, char relpersistence);
static bool ATPrepChangePersistence(Relation rel, bool toLogged);
static void ATChangeIndexesPersistence(Oid relid, char relpersistence);
static void ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel,
char *tablespacename, LOCKMODE lockmode);
static void ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode);
@ -3174,19 +3174,19 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
break;
case AT_SetLogged: /* SET LOGGED */
ATSimplePermissions(rel, ATT_TABLE);
tab->chgLoggedness = ATPrepChangeLoggedness(rel, true);
tab->chgPersistence = ATPrepChangePersistence(rel, true);
tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
/* force rewrite if necessary */
if (tab->chgLoggedness)
if (tab->chgPersistence)
tab->rewrite = true;
pass = AT_PASS_MISC;
break;
case AT_SetUnLogged: /* SET UNLOGGED */
ATSimplePermissions(rel, ATT_TABLE);
tab->chgLoggedness = ATPrepChangeLoggedness(rel, false);
tab->chgPersistence = ATPrepChangePersistence(rel, false);
tab->newrelpersistence = RELPERSISTENCE_UNLOGGED;
/* force rewrite if necessary */
if (tab->chgLoggedness)
if (tab->chgPersistence)
tab->rewrite = true;
pass = AT_PASS_MISC;
break;
@ -3618,6 +3618,13 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
* We only need to rewrite the table if at least one column needs to
* be recomputed, we are adding/removing the OID column, or we are
* changing its persistence.
*
* There are two reasons for requiring a rewrite when changing
* persistence: on one hand, we need to ensure that the buffers
* belonging to each of the two relations are marked with or without
* BM_PERMANENT properly. On the other hand, since rewriting creates
* and assigns a new relfilenode, we automatically create or drop an
* init fork for the relation as appropriate.
*/
if (tab->rewrite)
{
@ -3668,7 +3675,7 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
* Select persistence of transient table (same as original unless
* user requested a change)
*/
persistence = tab->chgLoggedness ?
persistence = tab->chgPersistence ?
tab->newrelpersistence : OldHeap->rd_rel->relpersistence;
heap_close(OldHeap, NoLock);
@ -3705,8 +3712,8 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
* because the rewrite step might read the indexes, and that would
* cause buffers for them to have the wrong setting.
*/
if (tab->chgLoggedness)
ATChangeIndexesLoggedness(tab->relid, tab->newrelpersistence);
if (tab->chgPersistence)
ATChangeIndexesPersistence(tab->relid, tab->newrelpersistence);
/*
* Swap the physical files of the old and new heaps, then rebuild
@ -4119,7 +4126,7 @@ ATGetQueueEntry(List **wqueue, Relation rel)
tab->relkind = rel->rd_rel->relkind;
tab->oldDesc = CreateTupleDescCopy(RelationGetDescr(rel));
tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
tab->chgLoggedness = false;
tab->chgPersistence = false;
*wqueue = lappend(*wqueue, tab);
@ -10678,7 +10685,7 @@ ATExecGenericOptions(Relation rel, List *options)
* checks are skipped), otherwise true.
*/
static bool
ATPrepChangeLoggedness(Relation rel, bool toLogged)
ATPrepChangePersistence(Relation rel, bool toLogged)
{
Relation pg_constraint;
HeapTuple tuple;
@ -10722,7 +10729,7 @@ ATPrepChangeLoggedness(Relation rel, bool toLogged)
/*
* Scan conrelid if changing to permanent, else confrelid. This also
* determines whether an useful index exists.
* determines whether a useful index exists.
*/
ScanKeyInit(&skey[0],
toLogged ? Anum_pg_constraint_conrelid :
@ -10792,7 +10799,7 @@ ATPrepChangeLoggedness(Relation rel, bool toLogged)
* given persistence.
*/
static void
ATChangeIndexesLoggedness(Oid relid, char relpersistence)
ATChangeIndexesPersistence(Oid relid, char relpersistence)
{
Relation rel;
Relation pg_class;