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Tweak some nbtree-related code comments.

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This commit is contained in:
Peter Geoghegan
2019-03-29 12:29:05 -07:00
parent d85e0f366a
commit 9c7fb7e6d8
4 changed files with 11 additions and 11 deletions
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2
contrib/amcheck/verify_nbtree.c
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@ -1975,7 +1975,7 @@ bt_normalize_tuple(BtreeCheckState *state, IndexTuple itup)
/* /*
* Search for itup in index, starting from fast root page. itup must be a * Search for itup in index, starting from fast root page. itup must be a
* non-pivot tuple. This is only supported with heapkeyspace indexes, since * non-pivot tuple. This is only supported with heapkeyspace indexes, since
* we rely on having fully unique keys to find a match with only a signle * we rely on having fully unique keys to find a match with only a single
* visit to a leaf page, barring an interrupted page split, where we may have * visit to a leaf page, barring an interrupted page split, where we may have
* to move right. (A concurrent page split is impossible because caller must * to move right. (A concurrent page split is impossible because caller must
* be readonly caller.) * be readonly caller.)

3
src/backend/access/nbtree/nbtsearch.c
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@ -182,7 +182,8 @@ _bt_search(Relation rel, BTScanInsert key, Buffer *bufP, int access,
/* /*
* If we're asked to lock leaf in write mode, but didn't manage to, then * If we're asked to lock leaf in write mode, but didn't manage to, then
* relock. That may happen when the root page appears to be leaf. * relock. This should only happen when the root page is a leaf page (and
* the only page in the index other than the metapage).
*/ */
if (access == BT_WRITE && page_access == BT_READ) if (access == BT_WRITE && page_access == BT_READ)
{ {

6
src/backend/access/nbtree/nbtsort.c
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@ -835,7 +835,7 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup)
* the limit on the size of tuples inserted on the leaf level by the same * the limit on the size of tuples inserted on the leaf level by the same
* small amount. Enforce the new v4+ limit on the leaf level, and the old * small amount. Enforce the new v4+ limit on the leaf level, and the old
* limit on internal levels, since pivot tuples may need to make use of * limit on internal levels, since pivot tuples may need to make use of
* the resered space. This should never fail on internal pages. * the reserved space. This should never fail on internal pages.
*/ */
if (unlikely(itupsz > BTMaxItemSize(npage))) if (unlikely(itupsz > BTMaxItemSize(npage)))
_bt_check_third_page(wstate->index, wstate->heap, _bt_check_third_page(wstate->index, wstate->heap,
@ -907,8 +907,8 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup)
* choosing a split point here for a benefit that is bound to be * choosing a split point here for a benefit that is bound to be
* much smaller. * much smaller.
* *
* Since the truncated tuple is probably smaller than the * Since the truncated tuple is often smaller than the original
* original, it cannot just be copied in place (besides, we want * tuple, it cannot just be copied in place (besides, we want
* to actually save space on the leaf page). We delete the * to actually save space on the leaf page). We delete the
* original high key, and add our own truncated high key at the * original high key, and add our own truncated high key at the
* same offset. It's okay if the truncated tuple is slightly * same offset. It's okay if the truncated tuple is slightly

11
src/include/access/nbtree.h
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@ -219,7 +219,6 @@ typedef struct BTMetaPageData
#define P_FIRSTDATAKEY(opaque) (P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY) #define P_FIRSTDATAKEY(opaque) (P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY)
/* /*
*
* Notes on B-Tree tuple format, and key and non-key attributes: * Notes on B-Tree tuple format, and key and non-key attributes:
* *
* INCLUDE B-Tree indexes have non-key attributes. These are extra * INCLUDE B-Tree indexes have non-key attributes. These are extra
@ -321,7 +320,7 @@ typedef struct BTMetaPageData
/* /*
* Get/set number of attributes within B-tree index tuple. * Get/set number of attributes within B-tree index tuple.
* *
* Note that this does not include an implicit tiebreaker heap-TID * Note that this does not include an implicit tiebreaker heap TID
* attribute, if any. Note also that the number of key attributes must be * attribute, if any. Note also that the number of key attributes must be
* explicitly represented in all heapkeyspace pivot tuples. * explicitly represented in all heapkeyspace pivot tuples.
*/ */
@ -424,10 +423,10 @@ typedef struct BTStackData
typedef BTStackData *BTStack; typedef BTStackData *BTStack;
/* /*
* BTScanInsert is the btree-private state needed to find an initial position * BTScanInsertData is the btree-private state needed to find an initial
* for an indexscan, or to insert new tuples -- an "insertion scankey" (not to * position for an indexscan, or to insert new tuples -- an "insertion
* be confused with a search scankey). It's used to descend a B-Tree using * scankey" (not to be confused with a search scankey). It's used to descend
* _bt_search. * a B-Tree using _bt_search.
* *
* heapkeyspace indicates if we expect all keys in the index to be physically * heapkeyspace indicates if we expect all keys in the index to be physically
* unique because heap TID is used as a tiebreaker attribute, and if index may * unique because heap TID is used as a tiebreaker attribute, and if index may