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35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid[] = "@(#)bt_overflow.c 8.5 (Berkeley) 7/16/94";
37 #endif /* LIBC_SCCS and not lint */
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
41 #include <sys/param.h>
53 * Big key and data entries are stored on linked lists of pages. The initial
54 * reference is byte string stored with the key or data and is the page number
55 * and size. The actual record is stored in a chain of pages linked by the
56 * nextpg field of the PAGE header.
58 * The first page of the chain has a special property. If the record is used
59 * by an internal page, it cannot be deleted and the P_PRESERVE bit will be set
63 * A single DBT is written to each chain, so a lot of space on the last page
64 * is wasted. This is a fairly major bug for some data sets.
68 * __OVFL_GET -- Get an overflow key/data item.
72 * p: pointer to { pgno_t, u_int32_t }
73 * buf: storage address
77 * RET_ERROR, RET_SUCCESS
80 __ovfl_get(BTREE *t, void *p, size_t *ssz, void **buf, size_t *bufsz)
87 memmove(&pg, p, sizeof(pgno_t));
88 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
92 if (pg == P_INVALID || sz == 0)
95 /* Make the buffer bigger as necessary. */
97 *buf = reallocf(*buf, sz);
104 * Step through the linked list of pages, copying the data on each one
105 * into the buffer. Never copy more than the data's length.
107 plen = t->bt_psize - BTDATAOFF;
108 for (p = *buf;; p = (char *)p + nb, pg = h->nextpg) {
109 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
113 memmove(p, (char *)h + BTDATAOFF, nb);
114 mpool_put(t->bt_mp, h, 0);
119 return (RET_SUCCESS);
123 * __OVFL_PUT -- Store an overflow key/data item.
128 * pgno: storage page number
131 * RET_ERROR, RET_SUCCESS
134 __ovfl_put(BTREE *t, const DBT *dbt, pgno_t *pg)
143 * Allocate pages and copy the key/data record into them. Store the
144 * number of the first page in the chain.
146 plen = t->bt_psize - BTDATAOFF;
147 for (last = NULL, p = dbt->data, sz = dbt->size;;
148 p = (char *)p + plen, last = h) {
149 if ((h = __bt_new(t, &npg)) == NULL)
153 h->nextpg = h->prevpg = P_INVALID;
154 h->flags = P_OVERFLOW;
155 h->lower = h->upper = 0;
158 memmove((char *)h + BTDATAOFF, p, nb);
161 last->nextpg = h->pgno;
162 mpool_put(t->bt_mp, last, MPOOL_DIRTY);
166 if ((sz -= nb) == 0) {
167 mpool_put(t->bt_mp, h, MPOOL_DIRTY);
171 return (RET_SUCCESS);
175 * __OVFL_DELETE -- Delete an overflow chain.
179 * p: pointer to { pgno_t, u_int32_t }
182 * RET_ERROR, RET_SUCCESS
185 __ovfl_delete(BTREE *t, void *p)
192 memmove(&pg, p, sizeof(pgno_t));
193 memmove(&sz, (char *)p + sizeof(pgno_t), sizeof(u_int32_t));
196 if (pg == P_INVALID || sz == 0)
199 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
202 /* Don't delete chains used by internal pages. */
203 if (h->flags & P_PRESERVE) {
204 mpool_put(t->bt_mp, h, 0);
205 return (RET_SUCCESS);
208 /* Step through the chain, calling the free routine for each page. */
209 for (plen = t->bt_psize - BTDATAOFF;; sz -= plen) {
214 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
217 return (RET_SUCCESS);