MonetDB: Jul2021 - small fix of the transaction isolation, ie ma...

[Niels Nes]

Changeset: b37bb160cc9a for MonetDB
URL: https://dev.monetdb.org/hg/MonetDB/rev/b37bb160cc9a
Modified Files:
        sql/storage/bat/bat_storage.c
Branch: Jul2021
Log Message:

small fix of the transaction isolation, ie make sure we still read segments 
which are deleted by some active transaction, but not commited yet.


diffs (74 lines):

diff --git a/sql/storage/bat/bat_storage.c b/sql/storage/bat/bat_storage.c
--- a/sql/storage/bat/bat_storage.c
+++ b/sql/storage/bat/bat_storage.c
@@ -140,31 +140,31 @@ split_segment(segments *segs, segment *o
        if (start == o->start) {
                n->start = o->start;
                n->end = n->start + cnt;
-               o->start = n->end;
                n->next = o;
                if (segs->h == o)
                        segs->h = n;
                if (p)
                        p->next = n;
+               o->start = n->end;
                return n;
        } else if (start+cnt == o->end) {
                n->start = o->end - cnt;
                n->end = o->end;
-               o->end = n->start;
                n->next = o->next;
                o->next = n;
                if (segs->t == o)
                        segs->t = n;
+               o->end = n->start;
                return n;
        }
        /* 3 way split */
        n->start = start;
        n->end = o->end;
-       o->end = n->start;
        n->next = o->next;
        o->next = n;
        if (segs->t == o)
                segs->t = n;
+       o->end = n->start;
 
        segment *oo = o;
        o = n;
@@ -177,11 +177,11 @@ split_segment(segments *segs, segment *o
        n->deleted = oo->deleted;
        n->start = start+cnt;
        n->end = o->end;
-       o->end = n->start;
        n->next = o->next;
        o->next = n;
        if (segs->t == o)
                segs->t = n;
+       o->end = n->start;
        return o;
 }
 
@@ -517,7 +517,7 @@ segs_end( segments *segs, sql_trans *tr)
        segment *s = segs->h, *l = NULL;
 
        for(;s; s = s->next) {
-               if (VALID_4_READ(s->ts, tr))
+               if (VALID_4_READ(s->ts, tr) || (s->deleted && s->oldts && s->ts 
> TRANSACTION_ID_BASE && s->oldts < tr->ts))
                                l = s;
        }
        if (!l)
@@ -2301,8 +2301,12 @@ clear_del(sql_trans *tr, sql_table *t)
        if ((bat = bind_del_data(tr, t)) == NULL)
                return BUN_NONE;
        if (!isTempTable(t)) {
-               if (delete_range(tr, bat, 0, bat->segs->t->end) == LOG_ERR)
+               lock_table(tr->store, t->base.id);
+               if (delete_range(tr, bat, 0, bat->segs->t->end) == LOG_ERR) {
+                       unlock_table(tr->store, t->base.id);
                        return LOG_ERR;
+               }
+               unlock_table(tr->store, t->base.id);
        }
        if ((!inTransaction(tr, t) && !in_transaction && isGlobal(t)) || 
(!isNew(t) && isLocalTemp(t)))
                trans_add(tr, &t->base, bat, &tc_gc_del, &commit_update_del, 
isLocalTemp(t)?NULL:&log_update_del);
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