diff options
Diffstat (limited to 'src/include/utils/rel.h')
| -rw-r--r-- | src/include/utils/rel.h | 58 |
1 files changed, 44 insertions, 14 deletions
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h index ca6c0a5adfa..99e6351c037 100644 --- a/src/include/utils/rel.h +++ b/src/include/utils/rel.h @@ -15,6 +15,7 @@ #define REL_H #include "access/tupdesc.h" +#include "access/xlog.h" #include "catalog/pg_am.h" #include "catalog/pg_class.h" #include "catalog/pg_index.h" @@ -82,25 +83,43 @@ typedef struct RelationData /*---------- * rd_createSubid is the ID of the highest subtransaction the rel has - * survived into; or zero if the rel was not created in the current top - * transaction. This can be now be relied on, whereas previously it could - * be "forgotten" in earlier releases. Likewise, rd_newRelfilenodeSubid is - * the ID of the highest subtransaction the relfilenode change has - * survived into, or zero if not changed in the current transaction (or we - * have forgotten changing it). rd_newRelfilenodeSubid can be forgotten - * when a relation has multiple new relfilenodes within a single - * transaction, with one of them occurring in a subsequently aborted - * subtransaction, e.g. + * survived into or zero if the rel or its rd_node was created before the + * current top transaction. (IndexStmt.oldNode leads to the case of a new + * rel with an old rd_node.) rd_firstRelfilenodeSubid is the ID of the + * highest subtransaction an rd_node change has survived into or zero if + * rd_node matches the value it had at the start of the current top + * transaction. (Rolling back the subtransaction that + * rd_firstRelfilenodeSubid denotes would restore rd_node to the value it + * had at the start of the current top transaction. Rolling back any + * lower subtransaction would not.) Their accuracy is critical to + * RelationNeedsWAL(). + * + * rd_newRelfilenodeSubid is the ID of the highest subtransaction the + * most-recent relfilenode change has survived into or zero if not changed + * in the current transaction (or we have forgotten changing it). This + * field is accurate when non-zero, but it can be zero when a relation has + * multiple new relfilenodes within a single transaction, with one of them + * occurring in a subsequently aborted subtransaction, e.g. * BEGIN; * TRUNCATE t; * SAVEPOINT save; * TRUNCATE t; * ROLLBACK TO save; * -- rd_newRelfilenodeSubid is now forgotten + * + * If every rd_*Subid field is zero, they are read-only outside + * relcache.c. Files that trigger rd_node changes by updating + * pg_class.reltablespace and/or pg_class.relfilenode call + * RelationAssumeNewRelfilenode() to update rd_*Subid. + * + * rd_droppedSubid is the ID of the highest subtransaction that a drop of + * the rel has survived into. In entries visible outside relcache.c, this + * is always zero. */ SubTransactionId rd_createSubid; /* rel was created in current xact */ - SubTransactionId rd_newRelfilenodeSubid; /* new relfilenode assigned in - * current xact */ + SubTransactionId rd_newRelfilenodeSubid; /* highest subxact changing + * rd_node to current value */ + /* see end for rd_firstRelfilenodeSubid and rd_droppedSubid */ Form_pg_class rd_rel; /* RELATION tuple */ TupleDesc rd_att; /* tuple descriptor */ @@ -189,6 +208,10 @@ typedef struct RelationData /* use "struct" here to avoid needing to include pgstat.h: */ struct PgStat_TableStatus *pgstat_info; /* statistics collection area */ + + SubTransactionId rd_firstRelfilenodeSubid; /* highest subxact changing + * rd_node to any value */ + SubTransactionId rd_droppedSubid; /* dropped with another Subid set */ } RelationData; /* @@ -437,9 +460,16 @@ typedef struct ViewOptions /* * RelationNeedsWAL * True if relation needs WAL. - */ -#define RelationNeedsWAL(relation) \ - ((relation)->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT) + * + * Returns false if wal_level = minimal and this relation is created or + * truncated in the current transaction. See "Skipping WAL for New + * RelFileNode" in src/backend/access/transam/README. + */ +#define RelationNeedsWAL(relation) \ + ((relation)->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT && \ + (XLogIsNeeded() || \ + (relation->rd_createSubid == InvalidSubTransactionId && \ + relation->rd_firstRelfilenodeSubid == InvalidSubTransactionId))) /* * RelationUsesLocalBuffers |