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1 : /*------------------------------------------------------------------------- 2 : * 3 : * gist.h 4 : * The public API for GiST indexes. This API is exposed to 5 : * individuals implementing GiST indexes, so backward-incompatible 6 : * changes should be made with care. 7 : * 8 : * 9 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group 10 : * Portions Copyright (c) 1994, Regents of the University of California 11 : * 12 : * src/include/access/gist.h 13 : * 14 : *------------------------------------------------------------------------- 15 : */ 16 : #ifndef GIST_H 17 : #define GIST_H 18 : 19 : #include "access/itup.h" 20 : #include "access/stratnum.h" 21 : #include "access/transam.h" 22 : #include "access/xlog.h" 23 : #include "access/xlogdefs.h" 24 : #include "storage/block.h" 25 : #include "storage/bufpage.h" 26 : #include "utils/relcache.h" 27 : 28 : /* 29 : * amproc indexes for GiST indexes. 30 : */ 31 : #define GIST_CONSISTENT_PROC 1 32 : #define GIST_UNION_PROC 2 33 : #define GIST_COMPRESS_PROC 3 34 : #define GIST_DECOMPRESS_PROC 4 35 : #define GIST_PENALTY_PROC 5 36 : #define GIST_PICKSPLIT_PROC 6 37 : #define GIST_EQUAL_PROC 7 38 : #define GIST_DISTANCE_PROC 8 39 : #define GIST_FETCH_PROC 9 40 : #define GIST_OPTIONS_PROC 10 41 : #define GIST_SORTSUPPORT_PROC 11 42 : #define GIST_STRATNUM_PROC 12 43 : #define GISTNProcs 12 44 : 45 : /* 46 : * Page opaque data in a GiST index page. 47 : */ 48 : #define F_LEAF (1 << 0) /* leaf page */ 49 : #define F_DELETED (1 << 1) /* the page has been deleted */ 50 : #define F_TUPLES_DELETED (1 << 2) /* some tuples on the page were 51 : * deleted */ 52 : #define F_FOLLOW_RIGHT (1 << 3) /* page to the right has no downlink */ 53 : #define F_HAS_GARBAGE (1 << 4) /* some tuples on the page are dead, 54 : * but not deleted yet */ 55 : 56 : /* 57 : * NSN (node sequence number) is a special-purpose LSN which is stored on each 58 : * index page in GISTPageOpaqueData and updated only during page splits. By 59 : * recording the parent's LSN in GISTSearchItem.parentlsn, it is possible to 60 : * detect concurrent child page splits by checking if parentlsn < child's NSN, 61 : * and handle them properly. The child page's LSN is insufficient for this 62 : * purpose since it is updated for every page change. 63 : */ 64 : typedef XLogRecPtr GistNSN; 65 : 66 : /* 67 : * A fake LSN / NSN value used during index builds. Must be smaller than any 68 : * real or fake (unlogged) LSN generated after the index build completes so 69 : * that all splits are considered complete. 70 : */ 71 : #define GistBuildLSN ((XLogRecPtr) 1) 72 : 73 : /* 74 : * For on-disk compatibility with pre-9.3 servers, NSN is stored as two 75 : * 32-bit fields on disk, same as LSNs. 76 : */ 77 : typedef PageXLogRecPtr PageGistNSN; 78 : 79 : typedef struct GISTPageOpaqueData 80 : { 81 : PageGistNSN nsn; /* this value must change on page split */ 82 : BlockNumber rightlink; /* next page if any */ 83 : uint16 flags; /* see bit definitions above */ 84 : uint16 gist_page_id; /* for identification of GiST indexes */ 85 : } GISTPageOpaqueData; 86 : 87 : typedef GISTPageOpaqueData *GISTPageOpaque; 88 : 89 : /* 90 : * Maximum possible sizes for GiST index tuple and index key. Calculation is 91 : * based on assumption that GiST page should fit at least 4 tuples. In theory, 92 : * GiST index can be functional when page can fit 3 tuples. But that seems 93 : * rather inefficient, so we use a bit conservative estimate. 94 : * 95 : * The maximum size of index key is true for unicolumn index. Therefore, this 96 : * estimation should be used to figure out which maximum size of GiST index key 97 : * makes sense at all. For multicolumn indexes, user might be able to tune 98 : * key size using opclass parameters. 99 : */ 100 : #define GISTMaxIndexTupleSize \ 101 : MAXALIGN_DOWN((BLCKSZ - SizeOfPageHeaderData - sizeof(GISTPageOpaqueData)) / \ 102 : 4 - sizeof(ItemIdData)) 103 : 104 : #define GISTMaxIndexKeySize \ 105 : (GISTMaxIndexTupleSize - MAXALIGN(sizeof(IndexTupleData))) 106 : 107 : /* 108 : * The page ID is for the convenience of pg_filedump and similar utilities, 109 : * which otherwise would have a hard time telling pages of different index 110 : * types apart. It should be the last 2 bytes on the page. This is more or 111 : * less "free" due to alignment considerations. 112 : */ 113 : #define GIST_PAGE_ID 0xFF81 114 : 115 : /* 116 : * This is the Split Vector to be returned by the PickSplit method. 117 : * PickSplit should fill the indexes of tuples to go to the left side into 118 : * spl_left[], and those to go to the right into spl_right[] (note the method 119 : * is responsible for palloc'ing both of these arrays!). The tuple counts 120 : * go into spl_nleft/spl_nright, and spl_ldatum/spl_rdatum must be set to 121 : * the union keys for each side. 122 : * 123 : * If spl_ldatum_exists and spl_rdatum_exists are true, then we are performing 124 : * a "secondary split" using a non-first index column. In this case some 125 : * decisions have already been made about a page split, and the set of tuples 126 : * being passed to PickSplit is just the tuples about which we are undecided. 127 : * spl_ldatum/spl_rdatum then contain the union keys for the tuples already 128 : * chosen to go left or right. Ideally the PickSplit method should take those 129 : * keys into account while deciding what to do with the remaining tuples, ie 130 : * it should try to "build out" from those unions so as to minimally expand 131 : * them. If it does so, it should union the given tuples' keys into the 132 : * existing spl_ldatum/spl_rdatum values rather than just setting those values 133 : * from scratch, and then set spl_ldatum_exists/spl_rdatum_exists to false to 134 : * show it has done this. 135 : * 136 : * If the PickSplit method fails to clear spl_ldatum_exists/spl_rdatum_exists, 137 : * the core GiST code will make its own decision about how to merge the 138 : * secondary-split results with the previously-chosen tuples, and will then 139 : * recompute the union keys from scratch. This is a workable though often not 140 : * optimal approach. 141 : */ 142 : typedef struct GIST_SPLITVEC 143 : { 144 : OffsetNumber *spl_left; /* array of entries that go left */ 145 : int spl_nleft; /* size of this array */ 146 : Datum spl_ldatum; /* Union of keys in spl_left */ 147 : bool spl_ldatum_exists; /* true, if spl_ldatum already exists. */ 148 : 149 : OffsetNumber *spl_right; /* array of entries that go right */ 150 : int spl_nright; /* size of the array */ 151 : Datum spl_rdatum; /* Union of keys in spl_right */ 152 : bool spl_rdatum_exists; /* true, if spl_rdatum already exists. */ 153 : } GIST_SPLITVEC; 154 : 155 : /* 156 : * An entry on a GiST node. Contains the key, as well as its own 157 : * location (rel,page,offset) which can supply the matching pointer. 158 : * leafkey is a flag to tell us if the entry is in a leaf node. 159 : */ 160 : typedef struct GISTENTRY 161 : { 162 : Datum key; 163 : Relation rel; 164 : Page page; 165 : OffsetNumber offset; 166 : bool leafkey; 167 : } GISTENTRY; 168 : 169 : #define GistPageGetOpaque(page) ( (GISTPageOpaque) PageGetSpecialPointer(page) ) 170 : 171 : #define GistPageIsLeaf(page) ( GistPageGetOpaque(page)->flags & F_LEAF) 172 : #define GIST_LEAF(entry) (GistPageIsLeaf((entry)->page)) 173 : 174 : #define GistPageIsDeleted(page) ( GistPageGetOpaque(page)->flags & F_DELETED) 175 : 176 : #define GistTuplesDeleted(page) ( GistPageGetOpaque(page)->flags & F_TUPLES_DELETED) 177 : #define GistMarkTuplesDeleted(page) ( GistPageGetOpaque(page)->flags |= F_TUPLES_DELETED) 178 : #define GistClearTuplesDeleted(page) ( GistPageGetOpaque(page)->flags &= ~F_TUPLES_DELETED) 179 : 180 : #define GistPageHasGarbage(page) ( GistPageGetOpaque(page)->flags & F_HAS_GARBAGE) 181 : #define GistMarkPageHasGarbage(page) ( GistPageGetOpaque(page)->flags |= F_HAS_GARBAGE) 182 : #define GistClearPageHasGarbage(page) ( GistPageGetOpaque(page)->flags &= ~F_HAS_GARBAGE) 183 : 184 : #define GistFollowRight(page) ( GistPageGetOpaque(page)->flags & F_FOLLOW_RIGHT) 185 : #define GistMarkFollowRight(page) ( GistPageGetOpaque(page)->flags |= F_FOLLOW_RIGHT) 186 : #define GistClearFollowRight(page) ( GistPageGetOpaque(page)->flags &= ~F_FOLLOW_RIGHT) 187 : 188 : #define GistPageGetNSN(page) ( PageXLogRecPtrGet(GistPageGetOpaque(page)->nsn)) 189 : #define GistPageSetNSN(page, val) ( PageXLogRecPtrSet(GistPageGetOpaque(page)->nsn, val)) 190 : 191 : 192 : /* 193 : * On a deleted page, we store this struct. A deleted page doesn't contain any 194 : * tuples, so we don't use the normal page layout with line pointers. Instead, 195 : * this struct is stored right after the standard page header. pd_lower points 196 : * to the end of this struct. If we add fields to this struct in the future, we 197 : * can distinguish the old and new formats by pd_lower. 198 : */ 199 : typedef struct GISTDeletedPageContents 200 : { 201 : /* last xid which could see the page in a scan */ 202 : FullTransactionId deleteXid; 203 : } GISTDeletedPageContents; 204 : 205 : static inline void 206 162 : GistPageSetDeleted(Page page, FullTransactionId deletexid) 207 : { 208 : Assert(PageIsEmpty(page)); 209 : 210 162 : GistPageGetOpaque(page)->flags |= F_DELETED; 211 162 : ((PageHeader) page)->pd_lower = MAXALIGN(SizeOfPageHeaderData) + sizeof(GISTDeletedPageContents); 212 : 213 162 : ((GISTDeletedPageContents *) PageGetContents(page))->deleteXid = deletexid; 214 162 : } 215 : 216 : static inline FullTransactionId 217 0 : GistPageGetDeleteXid(Page page) 218 : { 219 : Assert(GistPageIsDeleted(page)); 220 : 221 : /* Is the deleteXid field present? */ 222 0 : if (((PageHeader) page)->pd_lower >= MAXALIGN(SizeOfPageHeaderData) + 223 : offsetof(GISTDeletedPageContents, deleteXid) + sizeof(FullTransactionId)) 224 : { 225 0 : return ((GISTDeletedPageContents *) PageGetContents(page))->deleteXid; 226 : } 227 : else 228 0 : return FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId); 229 : } 230 : 231 : /* 232 : * Vector of GISTENTRY structs; user-defined methods union and picksplit 233 : * take it as one of their arguments 234 : */ 235 : typedef struct 236 : { 237 : int32 n; /* number of elements */ 238 : GISTENTRY vector[FLEXIBLE_ARRAY_MEMBER]; 239 : } GistEntryVector; 240 : 241 : #define GEVHDRSZ (offsetof(GistEntryVector, vector)) 242 : 243 : /* 244 : * macro to initialize a GISTENTRY 245 : */ 246 : #define gistentryinit(e, k, r, pg, o, l) \ 247 : do { (e).key = (k); (e).rel = (r); (e).page = (pg); \ 248 : (e).offset = (o); (e).leafkey = (l); } while (0) 249 : 250 : extern StrategyNumber GistTranslateStratnum(Oid opclass, StrategyNumber strat); 251 : 252 : #endif /* GIST_H */