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amcheck: Fix ordering bug in update_cached_xid_range()

The initialization order in update_cached_xid_range() was wrong, callingFullTransactionIdFromXidAndCtx() before setting->next_xid. FullTransactionIdFromXidAndCtx() uses ->next_xid.In most situations this will not cause visible issues, because the next callto update_cached_xid_range() will use a less wrong ->next_xid. It's rare thatxids advance fast enough for this to be a problem.Found while adding more asserts to the 64bit xid infrastructure.Reviewed-by: Mark Dilger <mark.dilger@enterprisedb.com>Discussion:https://postgr.es/m/20230108002923.cyoser3ttmt63bfn@awork3.anarazel.deBackpatch: 14-, where heapam verification was introduced

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contrib/amcheck
- verify_heapam.c

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`‎contrib/amcheck/verify_heapam.c`

Lines changed: 4 additions & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -1578,6 +1578,9 @@ FullTransactionIdFromXidAndCtx(TransactionId xid, const HeapCheckContext *ctx)`
`1578`	`1578`	`{`
`1579`	`1579`	`uint32epoch;`
`1580`	`1580`
	`1581`	`+Assert(TransactionIdIsNormal(ctx->next_xid));`
	`1582`	`+Assert(FullTransactionIdIsNormal(ctx->next_fxid));`
	`1583`	`+`
`1581`	`1584`	`if (!TransactionIdIsNormal(xid))`
`1582`	`1585`	`returnFullTransactionIdFromEpochAndXid(0,xid);`
`1583`	`1586`	`epoch=EpochFromFullTransactionId(ctx->next_fxid);`
`@@ -1599,8 +1602,8 @@ update_cached_xid_range(HeapCheckContext *ctx)`
`1599`	`1602`	`LWLockRelease(XidGenLock);`
`1600`	`1603`
`1601`	`1604`	`/* And compute alternate versions of the same */`
`1602`		`-ctx->oldest_fxid=FullTransactionIdFromXidAndCtx(ctx->oldest_xid,ctx);`
`1603`	`1605`	`ctx->next_xid=XidFromFullTransactionId(ctx->next_fxid);`
	`1606`	`+ctx->oldest_fxid=FullTransactionIdFromXidAndCtx(ctx->oldest_xid,ctx);`
`1604`	`1607`	`}`
`1605`	`1608`
`1606`	`1609`	`/*`

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Commita42f515

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`‎contrib/amcheck/verify_heapam.c`

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