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Indexes with INCLUDE columns and their support in B-tree

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This patch introduces INCLUDE clause to index definition.  This clause
specifies a list of columns which will be included as a non-key part in
the index.  The INCLUDE columns exist solely to allow more queries to
benefit from index-only scans.  Also, such columns don't need to have
appropriate operator classes.  Expressions are not supported as INCLUDE
columns since they cannot be used in index-only scans.

Index access methods supporting INCLUDE are indicated by amcaninclude flag
in IndexAmRoutine.  For now, only B-tree indexes support INCLUDE clause.

In B-tree indexes INCLUDE columns are truncated from pivot index tuples
(tuples located in non-leaf pages and high keys).  Therefore, B-tree indexes
now might have variable number of attributes.  This patch also provides
generic facility to support that: pivot tuples contain number of their
attributes in t_tid.ip_posid.  Free 13th bit of t_info is used for indicating
that.  This facility will simplify further support of index suffix truncation.
The changes of above are backward-compatible, pg_upgrade doesn't need special
handling of B-tree indexes for that.

Bump catalog version

Author: Anastasia Lubennikova with contribition by Alexander Korotkov and me
Reviewed by: Peter Geoghegan, Tomas Vondra, Antonin Houska, Jeff Janes,
			 David Rowley, Alexander Korotkov
Discussion: https://www.postgresql.org/message-id/flat/56168952.4010101@postgrespro.ru
This commit is contained in:
Teodor Sigaev
2018-04-07 23:00:39 +03:00
parent 01bb85169a
commit 8224de4f42
89 changed files with 2112 additions and 467 deletions
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91
src/include/access/nbtree.h
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@ -139,31 +139,6 @@ typedef struct BTMetaPageData
#define BTREE_DEFAULT_FILLFACTOR 90
#define BTREE_NONLEAF_FILLFACTOR 70
/*
* Test whether two btree entries are "the same".
*
* Old comments:
* In addition, we must guarantee that all tuples in the index are unique,
* in order to satisfy some assumptions in Lehman and Yao. The way that we
* do this is by generating a new OID for every insertion that we do in the
* tree. This adds eight bytes to the size of btree index tuples. Note
* that we do not use the OID as part of a composite key; the OID only
* serves as a unique identifier for a given index tuple (logical position
* within a page).
*
* New comments:
* actually, we must guarantee that all tuples in A LEVEL
* are unique, not in ALL INDEX. So, we can use the t_tid
* as unique identifier for a given index tuple (logical position
* within a level). - vadim 04/09/97
*/
#define BTTidSame(i1, i2) \
((ItemPointerGetBlockNumber(&(i1)) == ItemPointerGetBlockNumber(&(i2))) && \
(ItemPointerGetOffsetNumber(&(i1)) == ItemPointerGetOffsetNumber(&(i2))))
#define BTEntrySame(i1, i2) \
BTTidSame((i1)->t_tid, (i2)->t_tid)
/*
* In general, the btree code tries to localize its knowledge about
* page layout to a couple of routines. However, we need a special
@ -212,6 +187,68 @@ typedef struct BTMetaPageData
#define P_FIRSTDATAKEY(opaque) (P_RIGHTMOST(opaque) ? P_HIKEY : P_FIRSTKEY)
/*
* B-tree index with INCLUDE clause has non-key (included) attributes, which
* are used solely in index-only scans. Those non-key attributes are present
* in leaf index tuples which point to corresponding heap tuples. However,
* tree also contains "pivot" tuples. Pivot tuples are used for navigation
* during tree traversal. Pivot tuples include tuples on non-leaf pages and
* high key tuples. Such, tuples don't need to included attributes, because
* they have no use during tree traversal. This is why we truncate them in
* order to save some space. Therefore, B-tree index with INCLUDE clause
* contain tuples with variable number of attributes.
*
* In order to keep on-disk compatibility with upcoming suffix truncation of
* pivot tuples, we store number of attributes present inside tuple itself.
* Thankfully, offset number is always unused in pivot tuple. So, we use free
* bit of index tuple flags as sign that offset have alternative meaning: it
* stores number of keys present in index tuple (12 bit is far enough for that).
* And we have 4 bits reserved for future usage.
*
* Right now INDEX_ALT_TID_MASK is set only on truncation of non-key
* attributes of included indexes. But potentially every pivot index tuple
* might have INDEX_ALT_TID_MASK set. Then this tuple should have number of
* attributes correctly set in BT_N_KEYS_OFFSET_MASK, and in future it might
* use some bits of BT_RESERVED_OFFSET_MASK.
*
* Non-pivot tuples might also use bit of BT_RESERVED_OFFSET_MASK. Despite
* they store heap tuple offset, higher bits of offset are always free.
*/
#define INDEX_ALT_TID_MASK INDEX_AM_RESERVED_BIT /* flag indicating t_tid
* offset has an
* alternative meaning */
#define BT_RESERVED_OFFSET_MASK 0xF000 /* mask of bits in t_tid offset
* reserved for future usage */
#define BT_N_KEYS_OFFSET_MASK 0x0FFF /* mask of bits in t_tid offset
* holding number of attributes
* actually present in index tuple */
/* Acess to downlink block number */
#define BTreeInnerTupleGetDownLink(itup) \
ItemPointerGetBlockNumberNoCheck(&((itup)->t_tid))
#define BTreeInnerTupleSetDownLink(itup, blkno) \
ItemPointerSetBlockNumber(&((itup)->t_tid), (blkno))
/* Set number of attributes to B-tree index tuple overriding t_tid offset */
#define BTreeTupSetNAtts(itup, n) \
do { \
(itup)->t_info |= INDEX_ALT_TID_MASK; \
ItemPointerSetOffsetNumber(&(itup)->t_tid, n); \
} while(0)
/* Get number of attributes in B-tree index tuple */
#define BTreeTupGetNAtts(itup, index) \
( \
(itup)->t_info & INDEX_ALT_TID_MASK ? \
( \
AssertMacro((ItemPointerGetOffsetNumberNoCheck(&(itup)->t_tid) & BT_RESERVED_OFFSET_MASK) == 0), \
ItemPointerGetOffsetNumberNoCheck(&(itup)->t_tid) & BT_N_KEYS_OFFSET_MASK \
) \
: \
IndexRelationGetNumberOfAttributes(index) \
)
/*
* Operator strategy numbers for B-tree have been moved to access/stratnum.h,
* because many places need to use them in ScanKeyInit() calls.
@ -265,7 +302,7 @@ typedef struct BTStackData
{
BlockNumber bts_blkno;
OffsetNumber bts_offset;
IndexTupleData bts_btentry;
BlockNumber bts_btentry;
struct BTStackData *bts_parent;
} BTStackData;
@ -524,6 +561,7 @@ extern bool _bt_first(IndexScanDesc scan, ScanDirection dir);
extern bool _bt_next(IndexScanDesc scan, ScanDirection dir);
extern Buffer _bt_get_endpoint(Relation rel, uint32 level, bool rightmost,
Snapshot snapshot);
extern bool _bt_check_natts(Relation index, Page page, OffsetNumber offnum);
/*
* prototypes for functions in nbtutils.c
@ -552,6 +590,7 @@ extern bytea *btoptions(Datum reloptions, bool validate);
extern bool btproperty(Oid index_oid, int attno,
IndexAMProperty prop, const char *propname,
bool *res, bool *isnull);
extern IndexTuple _bt_truncate_tuple(Relation idxrel, IndexTuple olditup);
/*
* prototypes for functions in nbtvalidate.c