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Diffstat (limited to 'src/include/storage/itemid.h')
| -rw-r--r-- | src/include/storage/itemid.h | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/src/include/storage/itemid.h b/src/include/storage/itemid.h new file mode 100644 index 0000000..5b0229b --- /dev/null +++ b/src/include/storage/itemid.h @@ -0,0 +1,184 @@ +/*------------------------------------------------------------------------- + * + * itemid.h + * Standard POSTGRES buffer page item identifier/line pointer definitions. + * + * + * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/include/storage/itemid.h + * + *------------------------------------------------------------------------- + */ +#ifndef ITEMID_H +#define ITEMID_H + +/* + * A line pointer on a buffer page. See buffer page definitions and comments + * for an explanation of how line pointers are used. + * + * In some cases a line pointer is "in use" but does not have any associated + * storage on the page. By convention, lp_len == 0 in every line pointer + * that does not have storage, independently of its lp_flags state. + */ +typedef struct ItemIdData +{ + unsigned lp_off:15, /* offset to tuple (from start of page) */ + lp_flags:2, /* state of line pointer, see below */ + lp_len:15; /* byte length of tuple */ +} ItemIdData; + +typedef ItemIdData *ItemId; + +/* + * lp_flags has these possible states. An UNUSED line pointer is available + * for immediate re-use, the other states are not. + */ +#define LP_UNUSED 0 /* unused (should always have lp_len=0) */ +#define LP_NORMAL 1 /* used (should always have lp_len>0) */ +#define LP_REDIRECT 2 /* HOT redirect (should have lp_len=0) */ +#define LP_DEAD 3 /* dead, may or may not have storage */ + +/* + * Item offsets and lengths are represented by these types when + * they're not actually stored in an ItemIdData. + */ +typedef uint16 ItemOffset; +typedef uint16 ItemLength; + + +/* ---------------- + * support macros + * ---------------- + */ + +/* + * ItemIdGetLength + */ +#define ItemIdGetLength(itemId) \ + ((itemId)->lp_len) + +/* + * ItemIdGetOffset + */ +#define ItemIdGetOffset(itemId) \ + ((itemId)->lp_off) + +/* + * ItemIdGetFlags + */ +#define ItemIdGetFlags(itemId) \ + ((itemId)->lp_flags) + +/* + * ItemIdGetRedirect + * In a REDIRECT pointer, lp_off holds offset number for next line pointer + */ +#define ItemIdGetRedirect(itemId) \ + ((itemId)->lp_off) + +/* + * ItemIdIsValid + * True iff item identifier is valid. + * This is a pretty weak test, probably useful only in Asserts. + */ +#define ItemIdIsValid(itemId) PointerIsValid(itemId) + +/* + * ItemIdIsUsed + * True iff item identifier is in use. + */ +#define ItemIdIsUsed(itemId) \ + ((itemId)->lp_flags != LP_UNUSED) + +/* + * ItemIdIsNormal + * True iff item identifier is in state NORMAL. + */ +#define ItemIdIsNormal(itemId) \ + ((itemId)->lp_flags == LP_NORMAL) + +/* + * ItemIdIsRedirected + * True iff item identifier is in state REDIRECT. + */ +#define ItemIdIsRedirected(itemId) \ + ((itemId)->lp_flags == LP_REDIRECT) + +/* + * ItemIdIsDead + * True iff item identifier is in state DEAD. + */ +#define ItemIdIsDead(itemId) \ + ((itemId)->lp_flags == LP_DEAD) + +/* + * ItemIdHasStorage + * True iff item identifier has associated storage. + */ +#define ItemIdHasStorage(itemId) \ + ((itemId)->lp_len != 0) + +/* + * ItemIdSetUnused + * Set the item identifier to be UNUSED, with no storage. + * Beware of multiple evaluations of itemId! + */ +#define ItemIdSetUnused(itemId) \ +( \ + (itemId)->lp_flags = LP_UNUSED, \ + (itemId)->lp_off = 0, \ + (itemId)->lp_len = 0 \ +) + +/* + * ItemIdSetNormal + * Set the item identifier to be NORMAL, with the specified storage. + * Beware of multiple evaluations of itemId! + */ +#define ItemIdSetNormal(itemId, off, len) \ +( \ + (itemId)->lp_flags = LP_NORMAL, \ + (itemId)->lp_off = (off), \ + (itemId)->lp_len = (len) \ +) + +/* + * ItemIdSetRedirect + * Set the item identifier to be REDIRECT, with the specified link. + * Beware of multiple evaluations of itemId! + */ +#define ItemIdSetRedirect(itemId, link) \ +( \ + (itemId)->lp_flags = LP_REDIRECT, \ + (itemId)->lp_off = (link), \ + (itemId)->lp_len = 0 \ +) + +/* + * ItemIdSetDead + * Set the item identifier to be DEAD, with no storage. + * Beware of multiple evaluations of itemId! + */ +#define ItemIdSetDead(itemId) \ +( \ + (itemId)->lp_flags = LP_DEAD, \ + (itemId)->lp_off = 0, \ + (itemId)->lp_len = 0 \ +) + +/* + * ItemIdMarkDead + * Set the item identifier to be DEAD, keeping its existing storage. + * + * Note: in indexes, this is used as if it were a hint-bit mechanism; + * we trust that multiple processors can do this in parallel and get + * the same result. + */ +#define ItemIdMarkDead(itemId) \ +( \ + (itemId)->lp_flags = LP_DEAD \ +) + +#endif /* ITEMID_H */ |