Add comments for AlteredTableInfo->rel

The prior commit which introduced it was pretty squalid in terms of
code documentation, so add some comments.
This commit is contained in:
Alvaro Herrera 2021-03-25 16:07:15 -03:00
parent cd03c6e94b
commit cc121d5596
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@ -157,8 +157,16 @@ typedef struct AlteredTableInfo
Oid relid; /* Relation to work on */
char relkind; /* Its relkind */
TupleDesc oldDesc; /* Pre-modification tuple descriptor */
/* Transiently set during Phase 2, normally set to NULL */
/*
* Transiently set during Phase 2, normally set to NULL.
*
* ATRewriteCatalogs sets this when it starts, and closes when ATExecCmd
* returns control. This can be exploited by ATExecCmd subroutines to
* close/reopen across transaction boundaries.
*/
Relation rel;
/* Information saved by Phase 1 for Phase 2: */
List *subcmds[AT_NUM_PASSES]; /* Lists of AlterTableCmd */
/* Information saved by Phases 1/2 for Phase 3: */
@ -4577,7 +4585,9 @@ ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
continue;
/*
* Appropriate lock was obtained by phase 1, needn't get it again
* Open the relation and store it in tab. This allows subroutines
* close and reopen, if necessary. Appropriate lock was obtained
* by phase 1, needn't get it again.
*/
tab->rel = relation_open(tab->relid, NoLock);