Quelle  xid.c

/*-------------------------------------------------------------------------
 *
 * xid.c
 *   POSTGRES transaction identifier and command identifier datatypes.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *   src/backend/utils/adt/xid.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <limits.h>

#include "access/multixact.h"
#include "access/transam.h"
#include "access/xact.h"
#include "common/hashfn.h"
#include "common/int.h"
#include "libpq/pqformat.h"
#include "utils/builtins.h"
#include "utils/xid8.h"

#define PG_GETARG_COMMANDID(n)  DatumGetCommandId(PG_GETARG_DATUM(n))
#define PG_RETURN_COMMANDID(x)  return CommandIdGetDatum(x)


Datum
xidin(PG_FUNCTION_ARGS)
{
 char    *str = PG_GETARG_CSTRING(0);
 TransactionId result;

 result = uint32in_subr(str, NULL, "xid", fcinfo->context);
 PG_RETURN_TRANSACTIONID(result);
}

Datum
xidout(PG_FUNCTION_ARGS)
{
 TransactionId transactionId = PG_GETARG_TRANSACTIONID(0);
 char    *result = (char *) palloc(16);

 snprintf(result, 16, "%lu", (unsigned long) transactionId);
 PG_RETURN_CSTRING(result);
}

/*
 *  xidrecv   - converts external binary format to xid
 */
Datum
xidrecv(PG_FUNCTION_ARGS)
{
 StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);

 PG_RETURN_TRANSACTIONID((TransactionId) pq_getmsgint(buf, sizeof(TransactionId)));
}

/*
 *  xidsend   - converts xid to binary format
 */
Datum
xidsend(PG_FUNCTION_ARGS)
{
 TransactionId arg1 = PG_GETARG_TRANSACTIONID(0);
 StringInfoData buf;

 pq_begintypsend(&buf);
 pq_sendint32(&buf, arg1);
 PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

/*
 *  xideq   - are two xids equal?
 */
Datum
xideq(PG_FUNCTION_ARGS)
{
 TransactionId xid1 = PG_GETARG_TRANSACTIONID(0);
 TransactionId xid2 = PG_GETARG_TRANSACTIONID(1);

 PG_RETURN_BOOL(TransactionIdEquals(xid1, xid2));
}

/*
 *  xidneq   - are two xids different?
 */
Datum
xidneq(PG_FUNCTION_ARGS)
{
 TransactionId xid1 = PG_GETARG_TRANSACTIONID(0);
 TransactionId xid2 = PG_GETARG_TRANSACTIONID(1);

 PG_RETURN_BOOL(!TransactionIdEquals(xid1, xid2));
}

Datum
hashxid(PG_FUNCTION_ARGS)
{
 return hash_uint32(PG_GETARG_TRANSACTIONID(0));
}

Datum
hashxidextended(PG_FUNCTION_ARGS)
{
 return hash_uint32_extended(PG_GETARG_TRANSACTIONID(0), PG_GETARG_INT64(1));
}

/*
 *  xid_age   - compute age of an XID (relative to latest stable xid)
 */
Datum
xid_age(PG_FUNCTION_ARGS)
{
 TransactionId xid = PG_GETARG_TRANSACTIONID(0);
 TransactionId now = GetStableLatestTransactionId();

 /* Permanent XIDs are always infinitely old */
 if (!TransactionIdIsNormal(xid))
  PG_RETURN_INT32(INT_MAX);

 PG_RETURN_INT32((int32) (now - xid));
}

/*
 *  mxid_age   - compute age of a multi XID (relative to latest stable mxid)
 */
Datum
mxid_age(PG_FUNCTION_ARGS)
{
 TransactionId xid = PG_GETARG_TRANSACTIONID(0);
 MultiXactId now = ReadNextMultiXactId();

 if (!MultiXactIdIsValid(xid))
  PG_RETURN_INT32(INT_MAX);

 PG_RETURN_INT32((int32) (now - xid));
}

/*
 * xidComparator
 *  qsort comparison function for XIDs
 *
 * We can't use wraparound comparison for XIDs because that does not respect
 * the triangle inequality!  Any old sort order will do.
 */
int
xidComparator(const void *arg1, const void *arg2)
{
 TransactionId xid1 = *(const TransactionId *) arg1;
 TransactionId xid2 = *(const TransactionId *) arg2;

 return pg_cmp_u32(xid1, xid2);
}

/*
 * xidLogicalComparator
 *  qsort comparison function for XIDs
 *
 * This is used to compare only XIDs from the same epoch (e.g. for backends
 * running at the same time). So there must be only normal XIDs, so there's
 * no issue with triangle inequality.
 */
int
xidLogicalComparator(const void *arg1, const void *arg2)
{
 TransactionId xid1 = *(const TransactionId *) arg1;
 TransactionId xid2 = *(const TransactionId *) arg2;

 Assert(TransactionIdIsNormal(xid1));
 Assert(TransactionIdIsNormal(xid2));

 if (TransactionIdPrecedes(xid1, xid2))
  return -1;

 if (TransactionIdPrecedes(xid2, xid1))
  return 1;

 return 0;
}

Datum
xid8toxid(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid = PG_GETARG_FULLTRANSACTIONID(0);

 PG_RETURN_TRANSACTIONID(XidFromFullTransactionId(fxid));
}

Datum
xid8in(PG_FUNCTION_ARGS)
{
 char    *str = PG_GETARG_CSTRING(0);
 uint64  result;

 result = uint64in_subr(str, NULL, "xid8", fcinfo->context);
 PG_RETURN_FULLTRANSACTIONID(FullTransactionIdFromU64(result));
}

Datum
xid8out(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid = PG_GETARG_FULLTRANSACTIONID(0);
 char    *result = (char *) palloc(21);

 snprintf(result, 21, UINT64_FORMAT, U64FromFullTransactionId(fxid));
 PG_RETURN_CSTRING(result);
}

Datum
xid8recv(PG_FUNCTION_ARGS)
{
 StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
 uint64  value;

 value = (uint64) pq_getmsgint64(buf);
 PG_RETURN_FULLTRANSACTIONID(FullTransactionIdFromU64(value));
}

Datum
xid8send(PG_FUNCTION_ARGS)
{
 FullTransactionId arg1 = PG_GETARG_FULLTRANSACTIONID(0);
 StringInfoData buf;

 pq_begintypsend(&buf);
 pq_sendint64(&buf, (uint64) U64FromFullTransactionId(arg1));
 PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

Datum
xid8eq(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 PG_RETURN_BOOL(FullTransactionIdEquals(fxid1, fxid2));
}

Datum
xid8ne(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 PG_RETURN_BOOL(!FullTransactionIdEquals(fxid1, fxid2));
}

Datum
xid8lt(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 PG_RETURN_BOOL(FullTransactionIdPrecedes(fxid1, fxid2));
}

Datum
xid8gt(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 PG_RETURN_BOOL(FullTransactionIdFollows(fxid1, fxid2));
}

Datum
xid8le(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 PG_RETURN_BOOL(FullTransactionIdPrecedesOrEquals(fxid1, fxid2));
}

Datum
xid8ge(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 PG_RETURN_BOOL(FullTransactionIdFollowsOrEquals(fxid1, fxid2));
}

Datum
xid8cmp(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 if (FullTransactionIdFollows(fxid1, fxid2))
  PG_RETURN_INT32(1);
 else if (FullTransactionIdEquals(fxid1, fxid2))
  PG_RETURN_INT32(0);
 else
  PG_RETURN_INT32(-1);
}

Datum
hashxid8(PG_FUNCTION_ARGS)
{
 return hashint8(fcinfo);
}

Datum
hashxid8extended(PG_FUNCTION_ARGS)
{
 return hashint8extended(fcinfo);
}

Datum
xid8_larger(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 if (FullTransactionIdFollows(fxid1, fxid2))
  PG_RETURN_FULLTRANSACTIONID(fxid1);
 else
  PG_RETURN_FULLTRANSACTIONID(fxid2);
}

Datum
xid8_smaller(PG_FUNCTION_ARGS)
{
 FullTransactionId fxid1 = PG_GETARG_FULLTRANSACTIONID(0);
 FullTransactionId fxid2 = PG_GETARG_FULLTRANSACTIONID(1);

 if (FullTransactionIdPrecedes(fxid1, fxid2))
  PG_RETURN_FULLTRANSACTIONID(fxid1);
 else
  PG_RETURN_FULLTRANSACTIONID(fxid2);
}

/*****************************************************************************
 *  COMMAND IDENTIFIER ROUTINES            *
 *****************************************************************************/

/*
 *  cidin - converts CommandId to internal representation.
 */
Datum
cidin(PG_FUNCTION_ARGS)
{
 char    *str = PG_GETARG_CSTRING(0);
 CommandId result;

 result = uint32in_subr(str, NULL, "cid", fcinfo->context);
 PG_RETURN_COMMANDID(result);
}

/*
 *  cidout - converts a cid to external representation.
 */
Datum
cidout(PG_FUNCTION_ARGS)
{
 CommandId c = PG_GETARG_COMMANDID(0);
 char    *result = (char *) palloc(16);

 snprintf(result, 16, "%lu", (unsigned long) c);
 PG_RETURN_CSTRING(result);
}

/*
 *  cidrecv   - converts external binary format to cid
 */
Datum
cidrecv(PG_FUNCTION_ARGS)
{
 StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);

 PG_RETURN_COMMANDID((CommandId) pq_getmsgint(buf, sizeof(CommandId)));
}

/*
 *  cidsend   - converts cid to binary format
 */
Datum
cidsend(PG_FUNCTION_ARGS)
{
 CommandId arg1 = PG_GETARG_COMMANDID(0);
 StringInfoData buf;

 pq_begintypsend(&buf);
 pq_sendint32(&buf, arg1);
 PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

Datum
cideq(PG_FUNCTION_ARGS)
{
 CommandId arg1 = PG_GETARG_COMMANDID(0);
 CommandId arg2 = PG_GETARG_COMMANDID(1);

 PG_RETURN_BOOL(arg1 == arg2);
}

Datum
hashcid(PG_FUNCTION_ARGS)
{
 return hash_uint32(PG_GETARG_COMMANDID(0));
}

Datum
hashcidextended(PG_FUNCTION_ARGS)
{
 return hash_uint32_extended(PG_GETARG_COMMANDID(0), PG_GETARG_INT64(1));
}