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Use FullTransactionId for the transaction stack.

Provide GetTopFullTransactionId() and GetCurrentFullTransactionId().The intended users of these interfaces are access methods that usexids for visibility checks but don't want to have to go back and"freeze" existing references some time later before the 32 bit xidcounter wraps around.Use a new struct to serialize the transaction state for parallelquery, because FullTransactionId doesn't fit into the previousserialization scheme very well.Author: Thomas MunroReviewed-by: Heikki LinnakangasDiscussion:https://postgr.es/m/CAA4eK1%2BMv%2Bmb0HFfWM9Srtc6MVe160WFurXV68iAFMcagRZ0dQ%40mail.gmail.com

1 parent2fc7af5 commitad30805Copy full SHA for ad30805

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5 files changed

+170

-81

lines changed

src
- backend/access/transam
  - varsup.c
  - xact.c
- include/access
  - transam.h
  - xact.h
- tools/pgindent
  - typedefs.list

5 files changed

+170

-81

lines changed

`‎src/backend/access/transam/varsup.c`

Lines changed: 8 additions & 5 deletions

Original file line number	Diff line number	Diff line change
`@@ -35,7 +35,8 @@ VariableCache ShmemVariableCache = NULL;`
`35`	`35`
`36`	`36`
`37`	`37`	`/*`
`38`		`- * Allocate the next XID for a new transaction or subtransaction.`
	`38`	`+ * Allocate the next FullTransactionId for a new transaction or`
	`39`	`+ * subtransaction.`
`39`	`40`	`*`
`40`	`41`	`* The new XID is also stored into MyPgXact before returning.`
`41`	`42`	`*`
`@@ -44,9 +45,10 @@ VariableCache ShmemVariableCache = NULL;`
`44`	`45`	`* does something. So it is safe to do a database lookup if we want to`
`45`	`46`	`* issue a warning about XID wrap.`
`46`	`47`	`*/`
`47`		`-TransactionId`
	`48`	`+FullTransactionId`
`48`	`49`	`GetNewTransactionId(boolisSubXact)`
`49`	`50`	`{`
	`51`	`+FullTransactionIdfull_xid;`
`50`	`52`	`TransactionIdxid;`
`51`	`53`
`52`	`54`	`/*`
`@@ -64,7 +66,7 @@ GetNewTransactionId(bool isSubXact)`
`64`	`66`	`{`
`65`	`67`	`Assert(!isSubXact);`
`66`	`68`	`MyPgXact->xid=BootstrapTransactionId;`
`67`		`-returnBootstrapTransactionId;`
	`69`	`+returnFullTransactionIdFromEpochAndXid(0,BootstrapTransactionId);`
`68`	`70`	`}`
`69`	`71`
`70`	`72`	`/* safety check, we should never get this far in a HS standby */`
`@@ -73,7 +75,8 @@ GetNewTransactionId(bool isSubXact)`
`73`	`75`
`74`	`76`	`LWLockAcquire(XidGenLock,LW_EXCLUSIVE);`
`75`	`77`
`76`		`-xid=XidFromFullTransactionId(ShmemVariableCache->nextFullXid);`
	`78`	`+full_xid=ShmemVariableCache->nextFullXid;`
	`79`	`+xid=XidFromFullTransactionId(full_xid);`
`77`	`80`
`78`	`81`	`/*----------`
`79`	`82`	`* Check to see if it's safe to assign another XID. This protects against`
`@@ -232,7 +235,7 @@ GetNewTransactionId(bool isSubXact)`
`232`	`235`
`233`	`236`	`LWLockRelease(XidGenLock);`
`234`	`237`
`235`		`-returnxid;`
	`238`	`+returnfull_xid;`
`236`	`239`	`}`
`237`	`240`
`238`	`241`	`/*`

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Commitad30805

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`‎src/backend/access/transam/varsup.c`

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