printtup.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * printtup.c
 *    Routines to print out tuples to the destination (both frontend
 *    clients and standalone backends are supported here).
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/access/common/printtup.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/printtup.h"
#include "libpq/pqformat.h"
#include "libpq/protocol.h"
#include "tcop/pquery.h"
#include "utils/lsyscache.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"
 
 
static void printtup_startup(DestReceiver *self, int operation,
                             TupleDesc typeinfo);
static bool printtup(TupleTableSlot *slot, DestReceiver *self);
static void printtup_shutdown(DestReceiver *self);
static void printtup_destroy(DestReceiver *self);
 
/* ----------------------------------------------------------------
 *      printtup / debugtup support
 * ----------------------------------------------------------------
 */
 
/* ----------------
 *      Private state for a printtup destination object
 *
 * NOTE: finfo is the lookup info for either typoutput or typsend, whichever
 * we are using for this column.
 * ----------------
 */
typedef struct
{                               /* Per-attribute information */
    Oid         typoutput;      /* Oid for the type's text output fn */
    Oid         typsend;        /* Oid for the type's binary output fn */
    bool        typisvarlena;   /* is it varlena (ie possibly toastable)? */
    int16       format;         /* format code for this column */
    FmgrInfo    finfo;          /* Precomputed call info for output fn */
} PrinttupAttrInfo;
 
typedef struct
{
    DestReceiver pub;           /* publicly-known function pointers */
    Portal      portal;         /* the Portal we are printing from */
    bool        sendDescrip;    /* send RowDescription at startup? */
    TupleDesc   attrinfo;       /* The attr info we are set up for */
    int         nattrs;
    PrinttupAttrInfo *myinfo;   /* Cached info about each attr */
    StringInfoData buf;         /* output buffer (*not* in tmpcontext) */
    MemoryContext tmpcontext;   /* Memory context for per-row workspace */
} DR_printtup;
 
/* ----------------
 *      Initialize: create a DestReceiver for printtup
 * ----------------
 */
DestReceiver *
printtup_create_DR(CommandDest dest)
{
    DR_printtup *self = (DR_printtup *) palloc0(sizeof(DR_printtup));
 
    self->pub.receiveSlot = printtup;   /* might get changed later */
    self->pub.rStartup = printtup_startup;
    self->pub.rShutdown = printtup_shutdown;
    self->pub.rDestroy = printtup_destroy;
    self->pub.mydest = dest;
 
    /*
     * Send T message automatically if DestRemote, but not if
     * DestRemoteExecute
     */
    self->sendDescrip = (dest == DestRemote);
 
    self->attrinfo = NULL;
    self->nattrs = 0;
    self->myinfo = NULL;
    self->buf.data = NULL;
    self->tmpcontext = NULL;
 
    return (DestReceiver *) self;
}
 
/*
 * Set parameters for a DestRemote (or DestRemoteExecute) receiver
 */
void
SetRemoteDestReceiverParams(DestReceiver *self, Portal portal)
{
    DR_printtup *myState = (DR_printtup *) self;
 
    Assert(myState->pub.mydest == DestRemote ||
           myState->pub.mydest == DestRemoteExecute);
 
    myState->portal = portal;
}
 
static void
printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
{
    DR_printtup *myState = (DR_printtup *) self;
    Portal      portal = myState->portal;
 
    /*
     * Create I/O buffer to be used for all messages.  This cannot be inside
     * tmpcontext, since we want to re-use it across rows.
     */
    initStringInfo(&myState->buf);
 
    /*
     * Create a temporary memory context that we can reset once per row to
     * recover palloc'd memory.  This avoids any problems with leaks inside
     * datatype output routines, and should be faster than retail pfree's
     * anyway.
     */
    myState->tmpcontext = AllocSetContextCreate(CurrentMemoryContext,
                                                "printtup",
                                                ALLOCSET_DEFAULT_SIZES);
 
    /*
     * If we are supposed to emit row descriptions, then send the tuple
     * descriptor of the tuples.
     */
    if (myState->sendDescrip)
        SendRowDescriptionMessage(&myState->buf,
                                  typeinfo,
                                  FetchPortalTargetList(portal),
                                  portal->formats);
 
    /* ----------------
     * We could set up the derived attr info at this time, but we postpone it
     * until the first call of printtup, for 2 reasons:
     * 1. We don't waste time (compared to the old way) if there are no
     *    tuples at all to output.
     * 2. Checking in printtup allows us to handle the case that the tuples
     *    change type midway through (although this probably can't happen in
     *    the current executor).
     * ----------------
     */
}
 
/*
 * SendRowDescriptionMessage --- send a RowDescription message to the frontend
 *
 * Notes: the TupleDesc has typically been manufactured by ExecTypeFromTL()
 * or some similar function; it does not contain a full set of fields.
 * The targetlist will be NIL when executing a utility function that does
 * not have a plan.  If the targetlist isn't NIL then it is a Query node's
 * targetlist; it is up to us to ignore resjunk columns in it.  The formats[]
 * array pointer might be NULL (if we are doing Describe on a prepared stmt);
 * send zeroes for the format codes in that case.
 */
void
SendRowDescriptionMessage(StringInfo buf, TupleDesc typeinfo,
                          List *targetlist, int16 *formats)
{
    int         natts = typeinfo->natts;
    int         i;
    ListCell   *tlist_item = list_head(targetlist);
 
    /* tuple descriptor message type */
    pq_beginmessage_reuse(buf, PqMsg_RowDescription);
    /* # of attrs in tuples */
    pq_sendint16(buf, natts);
 
    /*
     * Preallocate memory for the entire message to be sent. That allows to
     * use the significantly faster inline pqformat.h functions and to avoid
     * reallocations.
     *
     * Have to overestimate the size of the column-names, to account for
     * character set overhead.
     */
    enlargeStringInfo(buf, (NAMEDATALEN * MAX_CONVERSION_GROWTH /* attname */
                            + sizeof(Oid)   /* resorigtbl */
                            + sizeof(AttrNumber)    /* resorigcol */
                            + sizeof(Oid)   /* atttypid */
                            + sizeof(int16) /* attlen */
                            + sizeof(int32) /* attypmod */
                            + sizeof(int16) /* format */
                            ) * natts);
 
    for (i = 0; i < natts; ++i)
    {
        Form_pg_attribute att = TupleDescAttr(typeinfo, i);
        Oid         atttypid = att->atttypid;
        int32       atttypmod = att->atttypmod;
        Oid         resorigtbl;
        AttrNumber  resorigcol;
        int16       format;
 
        /*
         * If column is a domain, send the base type and typmod instead.
         * Lookup before sending any ints, for efficiency.
         */
        atttypid = getBaseTypeAndTypmod(atttypid, &atttypmod);
 
        /* Do we have a non-resjunk tlist item? */
        while (tlist_item &&
               ((TargetEntry *) lfirst(tlist_item))->resjunk)
            tlist_item = lnext(targetlist, tlist_item);
        if (tlist_item)
        {
            TargetEntry *tle = (TargetEntry *) lfirst(tlist_item);
 
            resorigtbl = tle->resorigtbl;
            resorigcol = tle->resorigcol;
            tlist_item = lnext(targetlist, tlist_item);
        }
        else
        {
            /* No info available, so send zeroes */
            resorigtbl = 0;
            resorigcol = 0;
        }
 
        if (formats)
            format = formats[i];
        else
            format = 0;
 
        pq_writestring(buf, NameStr(att->attname));
        pq_writeint32(buf, resorigtbl);
        pq_writeint16(buf, resorigcol);
        pq_writeint32(buf, atttypid);
        pq_writeint16(buf, att->attlen);
        pq_writeint32(buf, atttypmod);
        pq_writeint16(buf, format);
    }
 
    pq_endmessage_reuse(buf);
}
 
/*
 * Get the lookup info that printtup() needs
 */
static void
printtup_prepare_info(DR_printtup *myState, TupleDesc typeinfo, int numAttrs)
{
    int16      *formats = myState->portal->formats;
    int         i;
 
    /* get rid of any old data */
    if (myState->myinfo)
        pfree(myState->myinfo);
    myState->myinfo = NULL;
 
    myState->attrinfo = typeinfo;
    myState->nattrs = numAttrs;
    if (numAttrs <= 0)
        return;
 
    myState->myinfo = (PrinttupAttrInfo *)
        palloc0(numAttrs * sizeof(PrinttupAttrInfo));
 
    for (i = 0; i < numAttrs; i++)
    {
        PrinttupAttrInfo *thisState = myState->myinfo + i;
        int16       format = (formats ? formats[i] : 0);
        Form_pg_attribute attr = TupleDescAttr(typeinfo, i);
 
        thisState->format = format;
        if (format == 0)
        {
            getTypeOutputInfo(attr->atttypid,
                              &thisState->typoutput,
                              &thisState->typisvarlena);
            fmgr_info(thisState->typoutput, &thisState->finfo);
        }
        else if (format == 1)
        {
            getTypeBinaryOutputInfo(attr->atttypid,
                                    &thisState->typsend,
                                    &thisState->typisvarlena);
            fmgr_info(thisState->typsend, &thisState->finfo);
        }
        else
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("unsupported format code: %d", format)));
    }
}
 
/* ----------------
 *      printtup --- send a tuple to the client
 *
 * Note: if you change this function, see also serializeAnalyzeReceive
 * in explain.c, which is meant to replicate the computations done here.
 * ----------------
 */
static bool
printtup(TupleTableSlot *slot, DestReceiver *self)
{
    TupleDesc   typeinfo = slot->tts_tupleDescriptor;
    DR_printtup *myState = (DR_printtup *) self;
    MemoryContext oldcontext;
    StringInfo  buf = &myState->buf;
    int         natts = typeinfo->natts;
    int         i;
 
    /* Set or update my derived attribute info, if needed */
    if (myState->attrinfo != typeinfo || myState->nattrs != natts)
        printtup_prepare_info(myState, typeinfo, natts);
 
    /* Make sure the tuple is fully deconstructed */
    slot_getallattrs(slot);
 
    /* Switch into per-row context so we can recover memory below */
    oldcontext = MemoryContextSwitchTo(myState->tmpcontext);
 
    /*
     * Prepare a DataRow message (note buffer is in per-query context)
     */
    pq_beginmessage_reuse(buf, PqMsg_DataRow);
 
    pq_sendint16(buf, natts);
 
    /*
     * send the attributes of this tuple
     */
    for (i = 0; i < natts; ++i)
    {
        PrinttupAttrInfo *thisState = myState->myinfo + i;
        Datum       attr = slot->tts_values[i];
 
        if (slot->tts_isnull[i])
        {
            pq_sendint32(buf, -1);
            continue;
        }
 
        /*
         * Here we catch undefined bytes in datums that are returned to the
         * client without hitting disk; see comments at the related check in
         * PageAddItem().  This test is most useful for uncompressed,
         * non-external datums, but we're quite likely to see such here when
         * testing new C functions.
         */
        if (thisState->typisvarlena)
            VALGRIND_CHECK_MEM_IS_DEFINED(DatumGetPointer(attr),
                                          VARSIZE_ANY(attr));
 
        if (thisState->format == 0)
        {
            /* Text output */
            char       *outputstr;
 
            outputstr = OutputFunctionCall(&thisState->finfo, attr);
            pq_sendcountedtext(buf, outputstr, strlen(outputstr));
        }
        else
        {
            /* Binary output */
            bytea      *outputbytes;
 
            outputbytes = SendFunctionCall(&thisState->finfo, attr);
            pq_sendint32(buf, VARSIZE(outputbytes) - VARHDRSZ);
            pq_sendbytes(buf, VARDATA(outputbytes),
                         VARSIZE(outputbytes) - VARHDRSZ);
        }
    }
 
    pq_endmessage_reuse(buf);
 
    /* Return to caller's context, and flush row's temporary memory */
    MemoryContextSwitchTo(oldcontext);
    MemoryContextReset(myState->tmpcontext);
 
    return true;
}
 
/* ----------------
 *      printtup_shutdown
 * ----------------
 */
static void
printtup_shutdown(DestReceiver *self)
{
    DR_printtup *myState = (DR_printtup *) self;
 
    if (myState->myinfo)
        pfree(myState->myinfo);
    myState->myinfo = NULL;
 
    myState->attrinfo = NULL;
 
    if (myState->buf.data)
        pfree(myState->buf.data);
    myState->buf.data = NULL;
 
    if (myState->tmpcontext)
        MemoryContextDelete(myState->tmpcontext);
    myState->tmpcontext = NULL;
}
 
/* ----------------
 *      printtup_destroy
 * ----------------
 */
static void
printtup_destroy(DestReceiver *self)
{
    pfree(self);
}
 
/* ----------------
 *      printatt
 * ----------------
 */
static void
printatt(unsigned attributeId,
         Form_pg_attribute attributeP,
         char *value)
{
    printf("\t%2d: %s%s%s%s\t(typeid = %u, len = %d, typmod = %d, byval = %c)\n",
           attributeId,
           NameStr(attributeP->attname),
           value != NULL ? " = \"" : "",
           value != NULL ? value : "",
           value != NULL ? "\"" : "",
           (unsigned int) (attributeP->atttypid),
           attributeP->attlen,
           attributeP->atttypmod,
           attributeP->attbyval ? 't' : 'f');
}
 
/* ----------------
 *      debugStartup - prepare to print tuples for an interactive backend
 * ----------------
 */
void
debugStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
{
    int         natts = typeinfo->natts;
    int         i;
 
    /*
     * show the return type of the tuples
     */
    for (i = 0; i < natts; ++i)
        printatt((unsigned) i + 1, TupleDescAttr(typeinfo, i), NULL);
    printf("\t----\n");
}
 
/* ----------------
 *      debugtup - print one tuple for an interactive backend
 * ----------------
 */
bool
debugtup(TupleTableSlot *slot, DestReceiver *self)
{
    TupleDesc   typeinfo = slot->tts_tupleDescriptor;
    int         natts = typeinfo->natts;
    int         i;
    Datum       attr;
    char       *value;
    bool        isnull;
    Oid         typoutput;
    bool        typisvarlena;
 
    for (i = 0; i < natts; ++i)
    {
        attr = slot_getattr(slot, i + 1, &isnull);
        if (isnull)
            continue;
        getTypeOutputInfo(TupleDescAttr(typeinfo, i)->atttypid,
                          &typoutput, &typisvarlena);
 
        value = OidOutputFunctionCall(typoutput, attr);
 
        printatt((unsigned) i + 1, TupleDescAttr(typeinfo, i), value);
    }
    printf("\t----\n");
 
    return true;
}