diff options
| -rw-r--r-- | src/backend/access/nbtree/nbtsplitloc.c | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/src/backend/access/nbtree/nbtsplitloc.c b/src/backend/access/nbtree/nbtsplitloc.c index 50d2faba29a..d045fe0d10c 100644 --- a/src/backend/access/nbtree/nbtsplitloc.c +++ b/src/backend/access/nbtree/nbtsplitloc.c @@ -196,11 +196,7 @@ _bt_findsplitloc(Relation rel, /* * Scan through the data items and calculate space usage for a split at - * each possible position. We start at the first data offset rather than - * the second data offset to handle the "newitemoff == first data offset" - * case (any other split whose firstoldonright is the first data offset - * can't be legal, though, and so won't actually end up being recorded in - * first loop iteration). + * each possible position */ olddataitemstoleft = 0; @@ -214,27 +210,38 @@ _bt_findsplitloc(Relation rel, itemsz = MAXALIGN(ItemIdGetLength(itemid)) + sizeof(ItemIdData); /* - * Will the new item go to left or right of split? + * When item offset number is not newitemoff, neither side of the + * split can be newitem. Record a split after the previous data item + * from original page, but before the current data item from original + * page. (_bt_recsplitloc() will reject the split when there are no + * previous data items, which we rely on.) */ - if (offnum > newitemoff) - _bt_recsplitloc(&state, offnum, true, olddataitemstoleft, itemsz); - else if (offnum < newitemoff) + if (offnum < newitemoff) _bt_recsplitloc(&state, offnum, false, olddataitemstoleft, itemsz); + else if (offnum > newitemoff) + _bt_recsplitloc(&state, offnum, true, olddataitemstoleft, itemsz); else { - /* may need to record a split on one or both sides of new item */ - _bt_recsplitloc(&state, offnum, true, olddataitemstoleft, itemsz); + /* + * Record a split after all "offnum < newitemoff" original page + * data items, but before newitem + */ _bt_recsplitloc(&state, offnum, false, olddataitemstoleft, itemsz); + + /* + * Record a split after newitem, but before data item from + * original page at offset newitemoff/current offset + */ + _bt_recsplitloc(&state, offnum, true, olddataitemstoleft, itemsz); } olddataitemstoleft += itemsz; } /* - * If the new item goes as the last item, record the split point that - * leaves all the old items on the left page, and the new item on the - * right page. This is required because a split that leaves the new item - * as the firstoldonright won't have been reached within the loop. + * Record a split after all original page data items, but before newitem. + * (Though only when it's possible that newitem will end up alone on new + * right page.) */ Assert(olddataitemstoleft == olddataitemstotal); if (newitemoff > maxoff) |