pg_lsn.c

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/*-------------------------------------------------------------------------
 *
 * pg_lsn.c
 *    Operations for the pg_lsn datatype.
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/pg_lsn.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "libpq/pqformat.h"
#include "utils/fmgrprotos.h"
#include "utils/numeric.h"
#include "utils/pg_lsn.h"
 
#define MAXPG_LSNLEN            17
#define MAXPG_LSNCOMPONENT  8
 
/*----------------------------------------------------------
 * Formatting and conversion routines.
 *---------------------------------------------------------*/
 
/*
 * Internal version of pg_lsn_in() with support for soft error reporting.
 */
XLogRecPtr
pg_lsn_in_safe(const char *str, Node *escontext)
{
    int         len1,
                len2;
    uint32      id,
                off;
    XLogRecPtr  result;
 
    /* Sanity check input format. */
    len1 = strspn(str, "0123456789abcdefABCDEF");
    if (len1 < 1 || len1 > MAXPG_LSNCOMPONENT || str[len1] != '/')
        goto syntax_error;
 
    len2 = strspn(str + len1 + 1, "0123456789abcdefABCDEF");
    if (len2 < 1 || len2 > MAXPG_LSNCOMPONENT || str[len1 + 1 + len2] != '\0')
        goto syntax_error;
 
    /* Decode result. */
    id = (uint32) strtoul(str, NULL, 16);
    off = (uint32) strtoul(str + len1 + 1, NULL, 16);
    result = ((uint64) id << 32) | off;
 
    return result;
 
syntax_error:
    ereturn(escontext, InvalidXLogRecPtr,
            (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
             errmsg("invalid input syntax for type %s: \"%s\"",
                    "pg_lsn", str)));
}
 
Datum
pg_lsn_in(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);
    XLogRecPtr  result;
 
    result = pg_lsn_in_safe(str, fcinfo->context);
 
    PG_RETURN_LSN(result);
}
 
Datum
pg_lsn_out(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn = PG_GETARG_LSN(0);
    char        buf[MAXPG_LSNLEN + 1];
    char       *result;
 
    snprintf(buf, sizeof buf, "%X/%08X", LSN_FORMAT_ARGS(lsn));
    result = pstrdup(buf);
    PG_RETURN_CSTRING(result);
}
 
Datum
pg_lsn_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    XLogRecPtr  result;
 
    result = pq_getmsgint64(buf);
    PG_RETURN_LSN(result);
}
 
Datum
pg_lsn_send(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn = PG_GETARG_LSN(0);
    StringInfoData buf;
 
    pq_begintypsend(&buf);
    pq_sendint64(&buf, lsn);
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}
 
 
/*----------------------------------------------------------
 *  Operators for PostgreSQL LSNs
 *---------------------------------------------------------*/
 
Datum
pg_lsn_eq(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_BOOL(lsn1 == lsn2);
}
 
Datum
pg_lsn_ne(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_BOOL(lsn1 != lsn2);
}
 
Datum
pg_lsn_lt(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_BOOL(lsn1 < lsn2);
}
 
Datum
pg_lsn_gt(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_BOOL(lsn1 > lsn2);
}
 
Datum
pg_lsn_le(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_BOOL(lsn1 <= lsn2);
}
 
Datum
pg_lsn_ge(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_BOOL(lsn1 >= lsn2);
}
 
Datum
pg_lsn_larger(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_LSN((lsn1 > lsn2) ? lsn1 : lsn2);
}
 
Datum
pg_lsn_smaller(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
 
    PG_RETURN_LSN((lsn1 < lsn2) ? lsn1 : lsn2);
}
 
/* btree index opclass support */
Datum
pg_lsn_cmp(PG_FUNCTION_ARGS)
{
    XLogRecPtr  a = PG_GETARG_LSN(0);
    XLogRecPtr  b = PG_GETARG_LSN(1);
 
    if (a > b)
        PG_RETURN_INT32(1);
    else if (a == b)
        PG_RETURN_INT32(0);
    else
        PG_RETURN_INT32(-1);
}
 
/* hash index opclass support */
Datum
pg_lsn_hash(PG_FUNCTION_ARGS)
{
    /* We can use hashint8 directly */
    return hashint8(fcinfo);
}
 
Datum
pg_lsn_hash_extended(PG_FUNCTION_ARGS)
{
    return hashint8extended(fcinfo);
}
 
 
/*----------------------------------------------------------
 *  Arithmetic operators on PostgreSQL LSNs.
 *---------------------------------------------------------*/
 
Datum
pg_lsn_mi(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn1 = PG_GETARG_LSN(0);
    XLogRecPtr  lsn2 = PG_GETARG_LSN(1);
    char        buf[256];
    Datum       result;
 
    /* Output could be as large as plus or minus 2^63 - 1. */
    if (lsn1 < lsn2)
        snprintf(buf, sizeof buf, "-" UINT64_FORMAT, lsn2 - lsn1);
    else
        snprintf(buf, sizeof buf, UINT64_FORMAT, lsn1 - lsn2);
 
    /* Convert to numeric. */
    result = DirectFunctionCall3(numeric_in,
                                 CStringGetDatum(buf),
                                 ObjectIdGetDatum(0),
                                 Int32GetDatum(-1));
 
    return result;
}
 
/*
 * Add the number of bytes to pg_lsn, giving a new pg_lsn.
 * Must handle both positive and negative numbers of bytes.
 */
Datum
pg_lsn_pli(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn = PG_GETARG_LSN(0);
    Numeric     nbytes = PG_GETARG_NUMERIC(1);
    Datum       num;
    Datum       res;
    char        buf[32];
 
    if (numeric_is_nan(nbytes))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot add NaN to pg_lsn")));
 
    /* Convert to numeric */
    snprintf(buf, sizeof(buf), UINT64_FORMAT, lsn);
    num = DirectFunctionCall3(numeric_in,
                              CStringGetDatum(buf),
                              ObjectIdGetDatum(0),
                              Int32GetDatum(-1));
 
    /* Add two numerics */
    res = DirectFunctionCall2(numeric_add,
                              num,
                              NumericGetDatum(nbytes));
 
    /* Convert to pg_lsn */
    return DirectFunctionCall1(numeric_pg_lsn, res);
}
 
/*
 * Subtract the number of bytes from pg_lsn, giving a new pg_lsn.
 * Must handle both positive and negative numbers of bytes.
 */
Datum
pg_lsn_mii(PG_FUNCTION_ARGS)
{
    XLogRecPtr  lsn = PG_GETARG_LSN(0);
    Numeric     nbytes = PG_GETARG_NUMERIC(1);
    Datum       num;
    Datum       res;
    char        buf[32];
 
    if (numeric_is_nan(nbytes))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot subtract NaN from pg_lsn")));
 
    /* Convert to numeric */
    snprintf(buf, sizeof(buf), UINT64_FORMAT, lsn);
    num = DirectFunctionCall3(numeric_in,
                              CStringGetDatum(buf),
                              ObjectIdGetDatum(0),
                              Int32GetDatum(-1));
 
    /* Subtract two numerics */
    res = DirectFunctionCall2(numeric_sub,
                              num,
                              NumericGetDatum(nbytes));
 
    /* Convert to pg_lsn */
    return DirectFunctionCall1(numeric_pg_lsn, res);
}