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