printsimple.c

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/*-------------------------------------------------------------------------
 *
 * printsimple.c
 *    Routines to print out tuples containing only a limited range of
 *    builtin types without catalog access.  This is intended for
 *    backends that don't have catalog access because they are not bound
 *    to a specific database, such as some walsender processes.  It
 *    doesn't handle standalone backends or protocol versions other than
 *    3.0, because we don't need such handling for current applications.
 *
 * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/access/common/printsimple.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/printsimple.h"
#include "catalog/pg_type.h"
#include "libpq/pqformat.h"
#include "utils/builtins.h"

/*
 * At startup time, send a RowDescription message.
 */
void
printsimple_startup(DestReceiver *self, int operation, TupleDesc tupdesc)
{
    StringInfoData buf;
    int         i;

    pq_beginmessage(&buf, 'T'); /* RowDescription */
    pq_sendint16(&buf, tupdesc->natts);

    for (i = 0; i < tupdesc->natts; ++i)
    {
        Form_pg_attribute attr = TupleDescAttr(tupdesc, i);

        pq_sendstring(&buf, NameStr(attr->attname));
        pq_sendint32(&buf, 0);  /* table oid */
        pq_sendint16(&buf, 0);  /* attnum */
        pq_sendint32(&buf, (int) attr->atttypid);
        pq_sendint16(&buf, attr->attlen);
        pq_sendint32(&buf, attr->atttypmod);
        pq_sendint16(&buf, 0);  /* format code */
    }

    pq_endmessage(&buf);
}

/*
 * For each tuple, send a DataRow message.
 */
bool
printsimple(TupleTableSlot *slot, DestReceiver *self)
{
    TupleDesc   tupdesc = slot->tts_tupleDescriptor;
    StringInfoData buf;
    int         i;

    /* Make sure the tuple is fully deconstructed */
    slot_getallattrs(slot);

    /* Prepare and send message */
    pq_beginmessage(&buf, 'D');
    pq_sendint16(&buf, tupdesc->natts);

    for (i = 0; i < tupdesc->natts; ++i)
    {
        Form_pg_attribute attr = TupleDescAttr(tupdesc, i);
        Datum       value;

        if (slot->tts_isnull[i])
        {
            pq_sendint32(&buf, -1);
            continue;
        }

        value = slot->tts_values[i];

        /*
         * We can't call the regular type output functions here because we
         * might not have catalog access.  Instead, we must hard-wire
         * knowledge of the required types.
         */
        switch (attr->atttypid)
        {
            case TEXTOID:
                {
                    text       *t = DatumGetTextPP(value);

                    pq_sendcountedtext(&buf,
                                       VARDATA_ANY(t),
                                       VARSIZE_ANY_EXHDR(t),
                                       false);
                }
                break;

            case INT4OID:
                {
                    int32       num = DatumGetInt32(value);
                    char        str[12];    /* sign, 10 digits and '\0' */
                    int         len;

                    len = pg_ltoa(num, str);
                    pq_sendcountedtext(&buf, str, len, false);
                }
                break;

            case INT8OID:
                {
                    int64       num = DatumGetInt64(value);
                    char        str[MAXINT8LEN + 1];
                    int         len;

                    len = pg_lltoa(num, str);
                    pq_sendcountedtext(&buf, str, len, false);
                }
                break;

            default:
                elog(ERROR, "unsupported type OID: %u", attr->atttypid);
        }
    }

    pq_endmessage(&buf);

    return true;
}