1 files changed, 101 insertions, 20 deletions

diff --git a/src/txn/txn_region.c b/src/txn/txn_region.c
index 6f43d45f..7fef66e6 100644
--- a/src/txn/txn_region.c
+++ b/src/txn/txn_region.c
@@ -1,7 +1,7 @@
 /*-
  * See the file LICENSE for redistribution information.
  *
- * Copyright (c) 1996, 2012 Oracle and/or its affiliates.  All rights reserved.
+ * Copyright (c) 1996, 2015 Oracle and/or its affiliates.  All rights reserved.
  *
  * $Id$
  */
@@ -13,6 +13,7 @@
 #include "dbinc/txn.h"
 
 static int __txn_init __P((ENV *, DB_TXNMGR *));
+static int lsn_hi_to_low __P((const void *, const void *));
 
 /*
  * __txn_open --
@@ -57,12 +58,30 @@ __txn_open(env)
 	env->tx_handle = mgr;
 	return (0);
 
-err:	env->tx_handle = NULL;
-	if (mgr->reginfo.addr != NULL)
-		(void)__env_region_detach(env, &mgr->reginfo, 0);
+err:	(void)__mutex_free(env, &mgr->mutex);
+	(void)__txn_region_detach(env, mgr);
 
-	(void)__mutex_free(env, &mgr->mutex);
-	__os_free(env, mgr);
+	return (ret);
+}
+
+/*
+ * __txn_region_detach --
+ *
+ * PUBLIC: int __txn_region_detach __P((ENV *, DB_TXNMGR *));
+ */
+int
+__txn_region_detach(env, mgr)
+	ENV *env;
+	DB_TXNMGR *mgr;
+{
+	int ret;
+
+	ret = 0;
+	if (mgr != NULL) {
+		ret = __env_region_detach(env, &mgr->reginfo, 0);
+		__os_free(env, mgr);
+		env->tx_handle = NULL;
+	}
 	return (ret);
 }
 
@@ -409,39 +428,101 @@ __txn_id_set(env, cur_txnid, max_txnid)
 }
 
 /*
- * __txn_oldest_reader --
- *	 Find the oldest "read LSN" of any active transaction'
- *	 MVCC changes older than this can safely be discarded from the cache.
+ * lsn_hi_to_low --
+ *	Compare lsns, sorting them from high to low. This is the opposite of
+ *	__rep_lsn_cmp.
+ */
+static int
+lsn_hi_to_low(lsn1, lsn2)
+	const void *lsn1, *lsn2;
+{
+	return (LOG_COMPARE((DB_LSN *)lsn2, (DB_LSN *)lsn1));
+}
+
+/*
+ * __txn_get_readers --
+ *	Find the read LSN of all active transactions.
+ *	MVCC versions older than the oldest active transaction can safely be
+ *	discarded from the cache. MVCC versions not quite so old can be
+ *      discarded if they are not visible to any active transaction.
  *
- * PUBLIC: int __txn_oldest_reader __P((ENV *, DB_LSN *));
+ * Returns:
+ *	An error code, or 0.
+ *	If 0 was returned, *readers has been filled in with an __os_malloc()'d
+ *	array of active transactions with read_lsns, sorted from newest
+ *      (largest) to oldest (smallest). *ntxnsp indicates how many are there.
+ *	The last lsn is that of the oldest active mvcc-supporting transaction.
+ *	The caller must __os_free() *readers whenever it is non-NULL.
+ *
+ * PUBLIC: int __txn_get_readers __P((ENV *, DB_LSN **, int *));
  */
+#define	TXN_READERS_SIZE	64 /* Initial number of LSNs to allocate. */
 int
-__txn_oldest_reader(env, lsnp)
+__txn_get_readers(env, readers, ntxnsp)
 	ENV *env;
-	DB_LSN *lsnp;
+	DB_LSN **readers;
+	int *ntxnsp;
 {
-	DB_LSN old_lsn;
+	DB_LSN current, *lsns;
 	DB_TXNMGR *mgr;
 	DB_TXNREGION *region;
 	TXN_DETAIL *td;
-	int ret;
+	int cmp, is_sorted, ret;
+	unsigned count, txnmax;
+
+	*ntxnsp = 0;
+	*readers = NULL;
 
 	if ((mgr = env->tx_handle) == NULL)
 		return (0);
 	region = mgr->reginfo.primary;
+	lsns = NULL;
+
+	if ((ret = __log_current_lsn_int(env, &current, NULL, NULL)) != 0)
+		return (ret);
 
-	if ((ret = __log_current_lsn_int(env, &old_lsn, NULL, NULL)) != 0)
+	txnmax = TXN_READERS_SIZE;
+	if ((ret = __os_malloc(env, txnmax * sizeof(lsns[0]), &lsns)) != 0)
 		return (ret);
 
 	TXN_SYSTEM_LOCK(env);
-	SH_TAILQ_FOREACH(td, &region->active_txn, links, __txn_detail)
-		if (LOG_COMPARE(&td->read_lsn, &old_lsn) < 0)
-			old_lsn = td->read_lsn;
+	/* The array always has at least the current lsn. */
+	lsns[0] = current;
+	count = 1;
+	is_sorted = TRUE;
 
-	*lsnp = old_lsn;
+	/*
+	 * Build up our array in most-recent (largest) to first-started (oldest)
+	 * order. Delete adjacent dups. Detect when the txns need to be sorted.
+	 */
+	SH_TAILQ_FOREACH(td, &region->active_txn, links, __txn_detail) {
+		if (IS_MAX_LSN(td->read_lsn) ||
+		    (cmp = LOG_COMPARE(&td->read_lsn, &lsns[count - 1])) == 0)
+			continue;
+		if (cmp > 0)
+			is_sorted = FALSE;
+		if (count >= txnmax) {
+			txnmax += txnmax;
+			if ((ret = __os_realloc(env,
+			    txnmax * sizeof(lsns[0]), &lsns)) != 0)
+				goto err;
+		}
+		lsns[count] = td->read_lsn;
+		count++;
+	}
+
+err:
 	TXN_SYSTEM_UNLOCK(env);
 
-	return (0);
+	if (ret != 0)
+		__os_free(env, lsns);
+	else {
+		if (!is_sorted)
+			qsort(lsns, count, sizeof(lsns[0]), lsn_hi_to_low);
+		*ntxnsp = (int)count;
+		*readers = lsns;
+	}
+	return (ret);
 }
 
 /*