/*------------------------------------------------------------------------- * * htup_details.h * POSTGRES heap tuple header definitions. * * * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/access/htup_details.h * *------------------------------------------------------------------------- */ #ifndef HTUP_DETAILS_H #define HTUP_DETAILS_H #include "access/htup.h" #include "access/transam.h" #include "access/tupdesc.h" #include "access/tupmacs.h" #include "storage/bufpage.h" /* * MaxTupleAttributeNumber limits the number of (user) columns in a tuple. * The key limit on this value is that the size of the fixed overhead for * a tuple, plus the size of the null-values bitmap (at 1 bit per column), * plus MAXALIGN alignment, must fit into t_hoff which is uint8. On most * machines the upper limit without making t_hoff wider would be a little * over 1700. We use round numbers here and for MaxHeapAttributeNumber * so that alterations in HeapTupleHeaderData layout won't change the * supported max number of columns. */ #define MaxTupleAttributeNumber 1664 /* 8 * 208 */ /* * MaxHeapAttributeNumber limits the number of (user) columns in a table. * This should be somewhat less than MaxTupleAttributeNumber. It must be * at least one less, else we will fail to do UPDATEs on a maximal-width * table (because UPDATE has to form working tuples that include CTID). * In practice we want some additional daylight so that we can gracefully * support operations that add hidden "resjunk" columns, for example * SELECT * FROM wide_table ORDER BY foo, bar, baz. * In any case, depending on column data types you will likely be running * into the disk-block-based limit on overall tuple size if you have more * than a thousand or so columns. TOAST won't help. */ #define MaxHeapAttributeNumber 1600 /* 8 * 200 */ /* * Heap tuple header. To avoid wasting space, the fields should be * laid out in such a way as to avoid structure padding. * * Datums of composite types (row types) share the same general structure * as on-disk tuples, so that the same routines can be used to build and * examine them. However the requirements are slightly different: a Datum * does not need any transaction visibility information, and it does need * a length word and some embedded type information. We can achieve this * by overlaying the xmin/cmin/xmax/cmax/xvac fields of a heap tuple * with the fields needed in the Datum case. Typically, all tuples built * in-memory will be initialized with the Datum fields; but when a tuple is * about to be inserted in a table, the transaction fields will be filled, * overwriting the datum fields. * * The overall structure of a heap tuple looks like: * fixed fields (HeapTupleHeaderData struct) * nulls bitmap (if HEAP_HASNULL is set in t_infomask) * alignment padding (as needed to make user data MAXALIGN'd) * object ID (if HEAP_HASOID_OLD is set in t_infomask, not created * anymore) * user data fields * * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in three * physical fields. Xmin and Xmax are always really stored, but Cmin, Cmax * and Xvac share a field. This works because we know that Cmin and Cmax * are only interesting for the lifetime of the inserting and deleting * transaction respectively. If a tuple is inserted and deleted in the same * transaction, we store a "combo" command id that can be mapped to the real * cmin and cmax, but only by use of local state within the originating * backend. See combocid.c for more details. Meanwhile, Xvac is only set by * old-style VACUUM FULL, which does not have any command sub-structure and so * does not need either Cmin or Cmax. (This requires that old-style VACUUM * FULL never try to move a tuple whose Cmin or Cmax is still interesting, * ie, an insert-in-progress or delete-in-progress tuple.) * * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid * is initialized with its own TID (location). If the tuple is ever updated, * its t_ctid is changed to point to the replacement version of the tuple. Or * if the tuple is moved from one partition to another, due to an update of * the partition key, t_ctid is set to a special value to indicate that * (see ItemPointerSetMovedPartitions). Thus, a tuple is the latest version * of its row iff XMAX is invalid or * t_ctid points to itself (in which case, if XMAX is valid, the tuple is * either locked or deleted). One can follow the chain of t_ctid links * to find the newest version of the row, unless it was moved to a different * partition. Beware however that VACUUM might * erase the pointed-to (newer) tuple before erasing the pointing (older) * tuple. Hence, when following a t_ctid link, it is necessary to check * to see if the referenced slot is empty or contains an unrelated tuple. * Check that the referenced tuple has XMIN equal to the referencing tuple's * XMAX to verify that it is actually the descendant version and not an * unrelated tuple stored into a slot recently freed by VACUUM. If either * check fails, one may assume that there is no live descendant version. * * t_ctid is sometimes used to store a speculative insertion token, instead * of a real TID. A speculative token is set on a tuple that's being * inserted, until the inserter is sure that it wants to go ahead with the * insertion. Hence a token should only be seen on a tuple with an XMAX * that's still in-progress, or invalid/aborted. The token is replaced with * the tuple's real TID when the insertion is confirmed. One should never * see a speculative insertion token while following a chain of t_ctid links, * because they are not used on updates, only insertions. * * Following the fixed header fields, the nulls bitmap is stored (beginning * at t_bits). The bitmap is *not* stored if t_infomask shows that there * are no nulls in the tuple. If an OID field is present (as indicated by * t_infomask), then it is stored just before the user data, which begins at * the offset shown by t_hoff. Note that t_hoff must be a multiple of * MAXALIGN. */ typedef struct HeapTupleFields { TransactionId t_xmin; /* inserting xact ID */ TransactionId t_xmax; /* deleting or locking xact ID */ union { CommandId t_cid; /* inserting or deleting command ID, or both */ TransactionId t_xvac; /* old-style VACUUM FULL xact ID */ } t_field3; } HeapTupleFields; typedef struct DatumTupleFields { int32 datum_len_; /* varlena header (do not touch directly!) */ int32 datum_typmod; /* -1, or identifier of a record type */ Oid datum_typeid; /* composite type OID, or RECORDOID */ /* * datum_typeid cannot be a domain over composite, only plain composite, * even if the datum is meant as a value of a domain-over-composite type. * This is in line with the general principle that CoerceToDomain does not * change the physical representation of the base type value. * * Note: field ordering is chosen with thought that Oid might someday * widen to 64 bits. */ } DatumTupleFields; struct HeapTupleHeaderData { union { HeapTupleFields t_heap; DatumTupleFields t_datum; } t_choice; ItemPointerData t_ctid; /* current TID of this or newer tuple (or a * speculative insertion token) */ /* Fields below here must match MinimalTupleData! */ #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK2 2 uint16 t_infomask2; /* number of attributes + various flags */ #define FIELDNO_HEAPTUPLEHEADERDATA_INFOMASK 3 uint16 t_infomask; /* various flag bits, see below */ #define FIELDNO_HEAPTUPLEHEADERDATA_HOFF 4 uint8 t_hoff; /* sizeof header incl. bitmap, padding */ /* ^ - 23 bytes - ^ */ #define FIELDNO_HEAPTUPLEHEADERDATA_BITS 5 bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */ /* MORE DATA FOLLOWS AT END OF STRUCT */ }; /* typedef appears in htup.h */ #define SizeofHeapTupleHeader offsetof(HeapTupleHeaderData, t_bits) /* * information stored in t_infomask: */ #define HEAP_HASNULL 0x0001 /* has null attribute(s) */ #define HEAP_HASVARWIDTH 0x0002 /* has variable-width attribute(s) */ #define HEAP_HASEXTERNAL 0x0004 /* has external stored attribute(s) */ #define HEAP_HASOID_OLD 0x0008 /* has an object-id field */ #define HEAP_XMAX_KEYSHR_LOCK 0x0010 /* xmax is a key-shared locker */ #define HEAP_COMBOCID 0x0020 /* t_cid is a combo CID */ #define HEAP_XMAX_EXCL_LOCK 0x0040 /* xmax is exclusive locker */ #define HEAP_XMAX_LOCK_ONLY 0x0080 /* xmax, if valid, is only a locker */ /* xmax is a shared locker */ #define HEAP_XMAX_SHR_LOCK (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK) #define HEAP_LOCK_MASK (HEAP_XMAX_SHR_LOCK | HEAP_XMAX_EXCL_LOCK | \ HEAP_XMAX_KEYSHR_LOCK) #define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */ #define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */ #define HEAP_XMIN_FROZEN (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID) #define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */ #define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */ #define HEAP_XMAX_IS_MULTI 0x1000 /* t_xmax is a MultiXactId */ #define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */ #define HEAP_MOVED_OFF 0x4000 /* moved to another place by pre-9.0 * VACUUM FULL; kept for binary * upgrade support */ #define HEAP_MOVED_IN 0x8000 /* moved from another place by pre-9.0 * VACUUM FULL; kept for binary * upgrade support */ #define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN) #define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */ /* * A tuple is only locked (i.e. not updated by its Xmax) if the * HEAP_XMAX_LOCK_ONLY bit is set; or, for pg_upgrade's sake, if the Xmax is * not a multi and the EXCL_LOCK bit is set. * * See also HeapTupleHeaderIsOnlyLocked, which also checks for a possible * aborted updater transaction. * * Beware of multiple evaluations of the argument. */ #define HEAP_XMAX_IS_LOCKED_ONLY(infomask) \ (((infomask) & HEAP_XMAX_LOCK_ONLY) || \ (((infomask) & (HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK)) == HEAP_XMAX_EXCL_LOCK)) /* * A tuple that has HEAP_XMAX_IS_MULTI and HEAP_XMAX_LOCK_ONLY but neither of * HEAP_XMAX_EXCL_LOCK and HEAP_XMAX_KEYSHR_LOCK must come from a tuple that was * share-locked in 9.2 or earlier and then pg_upgrade'd. * * In 9.2 and prior, HEAP_XMAX_IS_MULTI was only set when there were multiple * FOR SHARE lockers of that tuple. That set HEAP_XMAX_LOCK_ONLY (with a * different name back then) but neither of HEAP_XMAX_EXCL_LOCK and * HEAP_XMAX_KEYSHR_LOCK. That combination is no longer possible in 9.3 and * up, so if we see that combination we know for certain that the tuple was * locked in an earlier release; since all such lockers are gone (they cannot * survive through pg_upgrade), such tuples can safely be considered not * locked. * * We must not resolve such multixacts locally, because the result would be * bogus, regardless of where they stand with respect to the current valid * multixact range. */ #define HEAP_LOCKED_UPGRADED(infomask) \ ( \ ((infomask) & HEAP_XMAX_IS_MULTI) != 0 && \ ((infomask) & HEAP_XMAX_LOCK_ONLY) != 0 && \ (((infomask) & (HEAP_XMAX_EXCL_LOCK | HEAP_XMAX_KEYSHR_LOCK)) == 0) \ ) /* * Use these to test whether a particular lock is applied to a tuple */ #define HEAP_XMAX_IS_SHR_LOCKED(infomask) \ (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_SHR_LOCK) #define HEAP_XMAX_IS_EXCL_LOCKED(infomask) \ (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_EXCL_LOCK) #define HEAP_XMAX_IS_KEYSHR_LOCKED(infomask) \ (((infomask) & HEAP_LOCK_MASK) == HEAP_XMAX_KEYSHR_LOCK) /* turn these all off when Xmax is to change */ #define HEAP_XMAX_BITS (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID | \ HEAP_XMAX_IS_MULTI | HEAP_LOCK_MASK | HEAP_XMAX_LOCK_ONLY) /* * information stored in t_infomask2: */ #define HEAP_NATTS_MASK 0x07FF /* 11 bits for number of attributes */ /* bits 0x1800 are available */ #define HEAP_KEYS_UPDATED 0x2000 /* tuple was updated and key cols * modified, or tuple deleted */ #define HEAP_HOT_UPDATED 0x4000 /* tuple was HOT-updated */ #define HEAP_ONLY_TUPLE 0x8000 /* this is heap-only tuple */ #define HEAP2_XACT_MASK 0xE000 /* visibility-related bits */ /* * HEAP_TUPLE_HAS_MATCH is a temporary flag used during hash joins. It is * only used in tuples that are in the hash table, and those don't need * any visibility information, so we can overlay it on a visibility flag * instead of using up a dedicated bit. */ #define HEAP_TUPLE_HAS_MATCH HEAP_ONLY_TUPLE /* tuple has a join match */ /* * HeapTupleHeader accessor macros * * Note: beware of multiple evaluations of "tup" argument. But the Set * macros evaluate their other argument only once. */ /* * HeapTupleHeaderGetRawXmin returns the "raw" xmin field, which is the xid * originally used to insert the tuple. However, the tuple might actually * be frozen (via HeapTupleHeaderSetXminFrozen) in which case the tuple's xmin * is visible to every snapshot. Prior to PostgreSQL 9.4, we actually changed * the xmin to FrozenTransactionId, and that value may still be encountered * on disk. */ #define HeapTupleHeaderGetRawXmin(tup) \ ( \ (tup)->t_choice.t_heap.t_xmin \ ) #define HeapTupleHeaderGetXmin(tup) \ ( \ HeapTupleHeaderXminFrozen(tup) ? \ FrozenTransactionId : HeapTupleHeaderGetRawXmin(tup) \ ) #define HeapTupleHeaderSetXmin(tup, xid) \ ( \ (tup)->t_choice.t_heap.t_xmin = (xid) \ ) #define HeapTupleHeaderXminCommitted(tup) \ ( \ ((tup)->t_infomask & HEAP_XMIN_COMMITTED) != 0 \ ) #define HeapTupleHeaderXminInvalid(tup) \ ( \ ((tup)->t_infomask & (HEAP_XMIN_COMMITTED|HEAP_XMIN_INVALID)) == \ HEAP_XMIN_INVALID \ ) #define HeapTupleHeaderXminFrozen(tup) \ ( \ ((tup)->t_infomask & (HEAP_XMIN_FROZEN)) == HEAP_XMIN_FROZEN \ ) #define HeapTupleHeaderSetXminCommitted(tup) \ ( \ AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \ ((tup)->t_infomask |= HEAP_XMIN_COMMITTED) \ ) #define HeapTupleHeaderSetXminInvalid(tup) \ ( \ AssertMacro(!HeapTupleHeaderXminCommitted(tup)), \ ((tup)->t_infomask |= HEAP_XMIN_INVALID) \ ) #define HeapTupleHeaderSetXminFrozen(tup) \ ( \ AssertMacro(!HeapTupleHeaderXminInvalid(tup)), \ ((tup)->t_infomask |= HEAP_XMIN_FROZEN) \ ) /* * HeapTupleHeaderGetRawXmax gets you the raw Xmax field. To find out the Xid * that updated a tuple, you might need to resolve the MultiXactId if certain * bits are set. HeapTupleHeaderGetUpdateXid checks those bits and takes care * to resolve the MultiXactId if necessary. This might involve multixact I/O, * so it should only be used if absolutely necessary. */ #define HeapTupleHeaderGetUpdateXid(tup) \ ( \ (!((tup)->t_infomask & HEAP_XMAX_INVALID) && \ ((tup)->t_infomask & HEAP_XMAX_IS_MULTI) && \ !((tup)->t_infomask & HEAP_XMAX_LOCK_ONLY)) ? \ HeapTupleGetUpdateXid(tup) \ : \ HeapTupleHeaderGetRawXmax(tup) \ ) #define HeapTupleHeaderGetRawXmax(tup) \ ( \ (tup)->t_choice.t_heap.t_xmax \ ) #define HeapTupleHeaderSetXmax(tup, xid) \ ( \ (tup)->t_choice.t_heap.t_xmax = (xid) \ ) /* * HeapTupleHeaderGetRawCommandId will give you what's in the header whether * it is useful or not. Most code should use HeapTupleHeaderGetCmin or * HeapTupleHeaderGetCmax instead, but note that those Assert that you can * get a legitimate result, ie you are in the originating transaction! */ #define HeapTupleHeaderGetRawCommandId(tup) \ ( \ (tup)->t_choice.t_heap.t_field3.t_cid \ ) /* SetCmin is reasonably simple since we never need a combo CID */ #define HeapTupleHeaderSetCmin(tup, cid) \ do { \ Assert(!((tup)->t_infomask & HEAP_MOVED)); \ (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \ (tup)->t_infomask &= ~HEAP_COMBOCID; \ } while (0) /* SetCmax must be used after HeapTupleHeaderAdjustCmax; see combocid.c */ #define HeapTupleHeaderSetCmax(tup, cid, iscombo) \ do { \ Assert(!((tup)->t_infomask & HEAP_MOVED)); \ (tup)->t_choice.t_heap.t_field3.t_cid = (cid); \ if (iscombo) \ (tup)->t_infomask |= HEAP_COMBOCID; \ else \ (tup)->t_infomask &= ~HEAP_COMBOCID; \ } while (0) #define HeapTupleHeaderGetXvac(tup) \ ( \ ((tup)->t_infomask & HEAP_MOVED) ? \ (tup)->t_choice.t_heap.t_field3.t_xvac \ : \ InvalidTransactionId \ ) #define HeapTupleHeaderSetXvac(tup, xid) \ do { \ Assert((tup)->t_infomask & HEAP_MOVED); \ (tup)->t_choice.t_heap.t_field3.t_xvac = (xid); \ } while (0) #define HeapTupleHeaderIsSpeculative(tup) \ ( \ (ItemPointerGetOffsetNumberNoCheck(&(tup)->t_ctid) == SpecTokenOffsetNumber) \ ) #define HeapTupleHeaderGetSpeculativeToken(tup) \ ( \ AssertMacro(HeapTupleHeaderIsSpeculative(tup)), \ ItemPointerGetBlockNumber(&(tup)->t_ctid) \ ) #define HeapTupleHeaderSetSpeculativeToken(tup, token) \ ( \ ItemPointerSet(&(tup)->t_ctid, token, SpecTokenOffsetNumber) \ ) #define HeapTupleHeaderIndicatesMovedPartitions(tup) \ ItemPointerIndicatesMovedPartitions(&(tup)->t_ctid) #define HeapTupleHeaderSetMovedPartitions(tup) \ ItemPointerSetMovedPartitions(&(tup)->t_ctid) #define HeapTupleHeaderGetDatumLength(tup) \ VARSIZE(tup) #define HeapTupleHeaderSetDatumLength(tup, len) \ SET_VARSIZE(tup, len) #define HeapTupleHeaderGetTypeId(tup) \ ( \ (tup)->t_choice.t_datum.datum_typeid \ ) #define HeapTupleHeaderSetTypeId(tup, typeid) \ ( \ (tup)->t_choice.t_datum.datum_typeid = (typeid) \ ) #define HeapTupleHeaderGetTypMod(tup) \ ( \ (tup)->t_choice.t_datum.datum_typmod \ ) #define HeapTupleHeaderSetTypMod(tup, typmod) \ ( \ (tup)->t_choice.t_datum.datum_typmod = (typmod) \ ) /* * Note that we stop considering a tuple HOT-updated as soon as it is known * aborted or the would-be updating transaction is known aborted. For best * efficiency, check tuple visibility before using this macro, so that the * INVALID bits will be as up to date as possible. */ #define HeapTupleHeaderIsHotUpdated(tup) \ ( \ ((tup)->t_infomask2 & HEAP_HOT_UPDATED) != 0 && \ ((tup)->t_infomask & HEAP_XMAX_INVALID) == 0 && \ !HeapTupleHeaderXminInvalid(tup) \ ) #define HeapTupleHeaderSetHotUpdated(tup) \ ( \ (tup)->t_infomask2 |= HEAP_HOT_UPDATED \ ) #define HeapTupleHeaderClearHotUpdated(tup) \ ( \ (tup)->t_infomask2 &= ~HEAP_HOT_UPDATED \ ) #define HeapTupleHeaderIsHeapOnly(tup) \ ( \ ((tup)->t_infomask2 & HEAP_ONLY_TUPLE) != 0 \ ) #define HeapTupleHeaderSetHeapOnly(tup) \ ( \ (tup)->t_infomask2 |= HEAP_ONLY_TUPLE \ ) #define HeapTupleHeaderClearHeapOnly(tup) \ ( \ (tup)->t_infomask2 &= ~HEAP_ONLY_TUPLE \ ) #define HeapTupleHeaderHasMatch(tup) \ ( \ ((tup)->t_infomask2 & HEAP_TUPLE_HAS_MATCH) != 0 \ ) #define HeapTupleHeaderSetMatch(tup) \ ( \ (tup)->t_infomask2 |= HEAP_TUPLE_HAS_MATCH \ ) #define HeapTupleHeaderClearMatch(tup) \ ( \ (tup)->t_infomask2 &= ~HEAP_TUPLE_HAS_MATCH \ ) #define HeapTupleHeaderGetNatts(tup) \ ((tup)->t_infomask2 & HEAP_NATTS_MASK) #define HeapTupleHeaderSetNatts(tup, natts) \ ( \ (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \ ) #define HeapTupleHeaderHasExternal(tup) \ (((tup)->t_infomask & HEAP_HASEXTERNAL) != 0) /* * BITMAPLEN(NATTS) - * Computes size of null bitmap given number of data columns. */ #define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8) /* * MaxHeapTupleSize is the maximum allowed size of a heap tuple, including * header and MAXALIGN alignment padding. Basically it's BLCKSZ minus the * other stuff that has to be on a disk page. Since heap pages use no * "special space", there's no deduction for that. * * NOTE: we allow for the ItemId that must point to the tuple, ensuring that * an otherwise-empty page can indeed hold a tuple of this size. Because * ItemIds and tuples have different alignment requirements, don't assume that * you can, say, fit 2 tuples of size MaxHeapTupleSize/2 on the same page. */ #define MaxHeapTupleSize (BLCKSZ - MAXALIGN(SizeOfPageHeaderData + sizeof(ItemIdData))) #define MinHeapTupleSize MAXALIGN(SizeofHeapTupleHeader) /* * MaxHeapTuplesPerPage is an upper bound on the number of tuples that can * fit on one heap page. (Note that indexes could have more, because they * use a smaller tuple header.) We arrive at the divisor because each tuple * must be maxaligned, and it must have an associated line pointer. * * Note: with HOT, there could theoretically be more line pointers (not actual * tuples) than this on a heap page. However we constrain the number of line * pointers to this anyway, to avoid excessive line-pointer bloat and not * require increases in the size of work arrays. */ #define MaxHeapTuplesPerPage \ ((int) ((BLCKSZ - SizeOfPageHeaderData) / \ (MAXALIGN(SizeofHeapTupleHeader) + sizeof(ItemIdData)))) /* * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of * data fields of char(n) and similar types. It need not have anything * directly to do with the *actual* upper limit of varlena values, which * is currently 1Gb (see TOAST structures in postgres.h). I've set it * at 10Mb which seems like a reasonable number --- tgl 8/6/00. */ #define MaxAttrSize (10 * 1024 * 1024) /* * MinimalTuple is an alternative representation that is used for transient * tuples inside the executor, in places where transaction status information * is not required, the tuple rowtype is known, and shaving off a few bytes * is worthwhile because we need to store many tuples. The representation * is chosen so that tuple access routines can work with either full or * minimal tuples via a HeapTupleData pointer structure. The access routines * see no difference, except that they must not access the transaction status * or t_ctid fields because those aren't there. * * For the most part, MinimalTuples should be accessed via TupleTableSlot * routines. These routines will prevent access to the "system columns" * and thereby prevent accidental use of the nonexistent fields. * * MinimalTupleData contains a length word, some padding, and fields matching * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so * that offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both * structs. This makes data alignment rules equivalent in both cases. * * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is * set to point MINIMAL_TUPLE_OFFSET bytes before the actual start of the * minimal tuple --- that is, where a full tuple matching the minimal tuple's * data would start. This trick is what makes the structs seem equivalent. * * Note that t_hoff is computed the same as in a full tuple, hence it includes * the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however. * * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data * other than the length word. tuplesort.c and tuplestore.c use this to avoid * writing the padding to disk. */ #define MINIMAL_TUPLE_OFFSET \ ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF) #define MINIMAL_TUPLE_PADDING \ ((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF) #define MINIMAL_TUPLE_DATA_OFFSET \ offsetof(MinimalTupleData, t_infomask2) struct MinimalTupleData { uint32 t_len; /* actual length of minimal tuple */ char mt_padding[MINIMAL_TUPLE_PADDING]; /* Fields below here must match HeapTupleHeaderData! */ uint16 t_infomask2; /* number of attributes + various flags */ uint16 t_infomask; /* various flag bits, see below */ uint8 t_hoff; /* sizeof header incl. bitmap, padding */ /* ^ - 23 bytes - ^ */ bits8 t_bits[FLEXIBLE_ARRAY_MEMBER]; /* bitmap of NULLs */ /* MORE DATA FOLLOWS AT END OF STRUCT */ }; /* typedef appears in htup.h */ #define SizeofMinimalTupleHeader offsetof(MinimalTupleData, t_bits) /* * GETSTRUCT - given a HeapTuple pointer, return address of the user data */ #define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff) /* * Accessor macros to be used with HeapTuple pointers. */ #define HeapTupleHasNulls(tuple) \ (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0) #define HeapTupleNoNulls(tuple) \ (!((tuple)->t_data->t_infomask & HEAP_HASNULL)) #define HeapTupleHasVarWidth(tuple) \ (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0) #define HeapTupleAllFixed(tuple) \ (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH)) #define HeapTupleHasExternal(tuple) \ (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0) #define HeapTupleIsHotUpdated(tuple) \ HeapTupleHeaderIsHotUpdated((tuple)->t_data) #define HeapTupleSetHotUpdated(tuple) \ HeapTupleHeaderSetHotUpdated((tuple)->t_data) #define HeapTupleClearHotUpdated(tuple) \ HeapTupleHeaderClearHotUpdated((tuple)->t_data) #define HeapTupleIsHeapOnly(tuple) \ HeapTupleHeaderIsHeapOnly((tuple)->t_data) #define HeapTupleSetHeapOnly(tuple) \ HeapTupleHeaderSetHeapOnly((tuple)->t_data) #define HeapTupleClearHeapOnly(tuple) \ HeapTupleHeaderClearHeapOnly((tuple)->t_data) /* prototypes for functions in common/heaptuple.c */ extern Size heap_compute_data_size(TupleDesc tupleDesc, Datum *values, bool *isnull); extern void heap_fill_tuple(TupleDesc tupleDesc, Datum *values, bool *isnull, char *data, Size data_size, uint16 *infomask, bits8 *bit); extern bool heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc); extern Datum nocachegetattr(HeapTuple tup, int attnum, TupleDesc att); extern Datum heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull); extern Datum getmissingattr(TupleDesc tupleDesc, int attnum, bool *isnull); extern HeapTuple heap_copytuple(HeapTuple tuple); extern void heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest); extern Datum heap_copy_tuple_as_datum(HeapTuple tuple, TupleDesc tupleDesc); extern HeapTuple heap_form_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull); extern HeapTuple heap_modify_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *replValues, bool *replIsnull, bool *doReplace); extern HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, int *replCols, Datum *replValues, bool *replIsnull); extern void heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc, Datum *values, bool *isnull); extern void heap_freetuple(HeapTuple htup); extern MinimalTuple heap_form_minimal_tuple(TupleDesc tupleDescriptor, Datum *values, bool *isnull); extern void heap_free_minimal_tuple(MinimalTuple mtup); extern MinimalTuple heap_copy_minimal_tuple(MinimalTuple mtup); extern HeapTuple heap_tuple_from_minimal_tuple(MinimalTuple mtup); extern MinimalTuple minimal_tuple_from_heap_tuple(HeapTuple htup); extern size_t varsize_any(void *p); extern HeapTuple heap_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc); extern MinimalTuple minimal_expand_tuple(HeapTuple sourceTuple, TupleDesc tupleDesc); #ifndef FRONTEND /* * fastgetattr * Fetch a user attribute's value as a Datum (might be either a * value, or a pointer into the data area of the tuple). * * This must not be used when a system attribute might be requested. * Furthermore, the passed attnum MUST be valid. Use heap_getattr() * instead, if in doubt. * * This gets called many times, so we macro the cacheable and NULL * lookups, and call nocachegetattr() for the rest. */ static inline Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull) { Assert(attnum > 0); *isnull = false; if (HeapTupleNoNulls(tup)) { Form_pg_attribute att; att = TupleDescAttr(tupleDesc, attnum - 1); if (att->attcacheoff >= 0) return fetchatt(att, (char *) tup->t_data + tup->t_data->t_hoff + att->attcacheoff); else return nocachegetattr(tup, attnum, tupleDesc); } else { if (att_isnull(attnum - 1, tup->t_data->t_bits)) { *isnull = true; return (Datum) NULL; } else return nocachegetattr(tup, attnum, tupleDesc); } } /* * heap_getattr * Extract an attribute of a heap tuple and return it as a Datum. * This works for either system or user attributes. The given attnum * is properly range-checked. * * If the field in question has a NULL value, we return a zero Datum * and set *isnull == true. Otherwise, we set *isnull == false. * * is the pointer to the heap tuple. is the attribute * number of the column (field) caller wants. is a * pointer to the structure describing the row and all its fields. * */ static inline Datum heap_getattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull) { if (attnum > 0) { if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data)) return getmissingattr(tupleDesc, attnum, isnull); else return fastgetattr(tup, attnum, tupleDesc, isnull); } else return heap_getsysattr(tup, attnum, tupleDesc, isnull); } #endif /* FRONTEND */ #endif /* HTUP_DETAILS_H */