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Add fast paths for cases when no serializable transactions are running.

Dan Ports

1 parent97e8346 commit02e6a11Copy full SHA for 02e6a11

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src/backend/storage/lmgr
- predicate.c

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+21

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`‎src/backend/storage/lmgr/predicate.c`

Lines changed: 21 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -2275,6 +2275,18 @@ PredicateLockTupleRowVersionLink(const Relation relation,`
`2275`	`2275`	`TransactionIdoldxmin,`
`2276`	`2276`	`newxmin;`
`2277`	`2277`
	`2278`	`+/*`
	`2279`	`+ * Bail out quickly if there are no serializable transactions`
	`2280`	`+ * running.`
	`2281`	`+ *`
	`2282`	`+ * It's safe to do this check without taking any additional`
	`2283`	`+ * locks. Even if a serializable transaction starts concurrently,`
	`2284`	`+ * we know it can't take any SIREAD locks on the modified tuple`
	`2285`	`+ * because the caller is holding the associated buffer page lock.`
	`2286`	`+ */`
	`2287`	`+if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))`
	`2288`	`+return;`
	`2289`	`+`
`2278`	`2290`	`oldblk=ItemPointerGetBlockNumber(&(oldTuple->t_self));`
`2279`	`2291`	`oldoff=ItemPointerGetOffsetNumber(&(oldTuple->t_self));`
`2280`	`2292`	`oldxmin=HeapTupleHeaderGetXmin(oldTuple->t_data);`
`@@ -2633,6 +2645,15 @@ PredicateLockPageSplit(const Relation relation, const BlockNumber oldblkno,`
`2633`	`2645`	`PREDICATELOCKTARGETTAGnewtargettag;`
`2634`	`2646`	`boolsuccess;`
`2635`	`2647`
	`2648`	`+/*`
	`2649`	`+ * Bail out quickly if there are no serializable transactions`
	`2650`	`+ * running. As with PredicateLockTupleRowVersionLink, it's safe to`
	`2651`	`+ * check this without taking locks because the caller is holding`
	`2652`	`+ * the buffer page lock.`
	`2653`	`+ */`
	`2654`	`+if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))`
	`2655`	`+return;`
	`2656`	`+`
`2636`	`2657`	`if (SkipSplitTracking(relation))`
`2637`	`2658`	`return;`
`2638`	`2659`

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Commit02e6a11

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`‎src/backend/storage/lmgr/predicate.c`

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