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Diffstat (limited to 'src/include/access/htup_details.h')
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diff --git a/src/include/access/htup_details.h b/src/include/access/htup_details.h new file mode 100644 index 0000000..aebb108 --- /dev/null +++ b/src/include/access/htup_details.h @@ -0,0 +1,819 @@ +/*------------------------------------------------------------------------- + * + * htup_details.h + * POSTGRES heap tuple header definitions. + * + * + * Portions Copyright (c) 1996-2020, 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) \ + (ItemPointerGetOffsetNumber(&(tup)->t_ctid) == MovedPartitionsOffsetNumber && \ + ItemPointerGetBlockNumberNoCheck(&(tup)->t_ctid) == MovedPartitionsBlockNumber) + +#define HeapTupleHeaderSetMovedPartitions(tup) \ + ItemPointerSet(&(tup)->t_ctid, MovedPartitionsBlockNumber, MovedPartitionsOffsetNumber) + +#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) + + +/* ---------------- + * 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. + * ---------------- + */ + +#if !defined(DISABLE_COMPLEX_MACRO) + +#define fastgetattr(tup, attnum, tupleDesc, isnull) \ +( \ + AssertMacro((attnum) > 0), \ + (*(isnull) = false), \ + HeapTupleNoNulls(tup) ? \ + ( \ + TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff >= 0 ? \ + ( \ + fetchatt(TupleDescAttr((tupleDesc), (attnum)-1), \ + (char *) (tup)->t_data + (tup)->t_data->t_hoff + \ + TupleDescAttr((tupleDesc), (attnum)-1)->attcacheoff)\ + ) \ + : \ + nocachegetattr((tup), (attnum), (tupleDesc)) \ + ) \ + : \ + ( \ + att_isnull((attnum)-1, (tup)->t_data->t_bits) ? \ + ( \ + (*(isnull) = true), \ + (Datum)NULL \ + ) \ + : \ + ( \ + nocachegetattr((tup), (attnum), (tupleDesc)) \ + ) \ + ) \ +) +#else /* defined(DISABLE_COMPLEX_MACRO) */ + +extern Datum fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, + bool *isnull); +#endif /* defined(DISABLE_COMPLEX_MACRO) */ + + +/* ---------------- + * 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. + * + * <tup> is the pointer to the heap tuple. <attnum> is the attribute + * number of the column (field) caller wants. <tupleDesc> is a + * pointer to the structure describing the row and all its fields. + * ---------------- + */ +#define heap_getattr(tup, attnum, tupleDesc, isnull) \ + ( \ + ((attnum) > 0) ? \ + ( \ + ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \ + getmissingattr((tupleDesc), (attnum), (isnull)) \ + : \ + fastgetattr((tup), (attnum), (tupleDesc), (isnull)) \ + ) \ + : \ + heap_getsysattr((tup), (attnum), (tupleDesc), (isnull)) \ + ) + + +/* 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); + +#endif /* HTUP_DETAILS_H */ |