/*
* __compact_rewrite --
* Return if a page needs to be re-written.
*/
static int
__compact_rewrite(WT_SESSION_IMPL *session, WT_REF *ref, int *skipp)
{
WT_BM *bm;
WT_DECL_RET;
WT_PAGE *page;
WT_PAGE_MODIFY *mod;
size_t addr_size;
const uint8_t *addr;
*skipp = 1; /* Default skip. */
bm = S2BT(session)->bm;
page = ref->page;
mod = page->modify;
/*
* Ignore the root: it may not have a replacement address, and besides,
* if anything else gets written, so will it.
*/
if (__wt_ref_is_root(ref))
return (0);
/* Ignore currently dirty pages, they will be written regardless. */
if (__wt_page_is_modified(page))
return (0);
/*
* If the page is clean, test the original addresses.
* If the page is a 1-to-1 replacement, test the replacement addresses.
* Ignore empty pages, they get merged into the parent.
*/
if (mod == NULL || F_ISSET(mod, WT_PM_REC_MASK) == 0) {
WT_RET(__wt_ref_info(session, ref, &addr, &addr_size, NULL));
if (addr == NULL)
return (0);
WT_RET(
bm->compact_page_skip(bm, session, addr, addr_size, skipp));
} else if (F_ISSET(mod, WT_PM_REC_MASK) == WT_PM_REC_REPLACE) {
/*
* The page's modification information can change underfoot if
* the page is being reconciled, lock the page down.
*/
WT_PAGE_LOCK(session, page);
ret = bm->compact_page_skip(bm, session,
mod->mod_replace.addr, mod->mod_replace.size, skipp);
WT_PAGE_UNLOCK(session, page);
WT_RET(ret);
}
return (0);
}
/*将多余的文件空间compact到合适的位置,如果ref在compact范围内，返回skip = 1,表示文件空间不能进行compact*/
static int __compact_rewrite(WT_SESSION_IMPL* session, WT_REF* ref, int* skipp)
{
WT_BM *bm;
WT_DECL_RET;
WT_PAGE *page;
WT_PAGE_MODIFY *mod;
size_t addr_size;
const uint8_t *addr;
*skipp = 1;
bm = S2BT(session)->bm;
page = ref->page;
mod = page->modify;
/*root page是不能被compact*/
if (__wt_ref_is_root(ref))
return 0;
/*ref指向的是个脏页，不进行compact*/
if (__wt_page_is_modified(page))
return (0);
/*假如page一已经被清空的，直接判断是否可以它的block空间compact*/
if (mod == NULL || F_ISSET(mod, WT_PM_REC_MASK) == 0) {
WT_RET(__wt_ref_info(session, ref, &addr, &addr_size, NULL));
if (addr == NULL)
return (0);
WT_RET(bm->compact_page_skip(bm, session, addr, addr_size, skipp));
}
else if (F_ISSET(mod, WT_PM_REC_MASK) == WT_PM_REC_REPLACE){ /*如果page空间是替换，那么进行替换block的compact操作判断*/
WT_PAGE_LOCK(session, page);
ret = bm->compact_page_skip(bm, session, mod->mod_replace.addr, mod->mod_replace.size, skipp);
WT_PAGE_UNLOCK(session, page);
WT_RET(ret);
}
return 0;
}
