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Add a new DestReceiver for printing tuples without catalog access.

If you create a DestReciver of type DestRemote and try to use it from
a replication connection that is not bound to a specific daabase, or
any other hypothetical type of backend that is not bound to a specific
database, it will fail because it doesn't have a pg_proc catalog to
look up properties of the types being printed.  In general, that's
an unavoidable problem, but we can hardwire the properties of a few
builtin types in order to support utility commands.  This new
DestReceiver of type DestRemoteSimple does just that.

Patch by me, reviewed by Michael Paquier.

Discussion: http://postgr.es/m/CA+TgmobNo4qz06wHEmy9DszAre3dYx-WNhHSCbU9SAwf+9Ft6g@mail.gmail.com
This commit is contained in:
Robert Haas
2017-01-24 16:53:56 -05:00
parent 7b4ac19982
commit a84069d935
5 changed files with 148 additions and 2 deletions

View File

@@ -0,0 +1,110 @@
/*-------------------------------------------------------------------------
*
* 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) 1996-2017, 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 "fmgr.h"
#include "libpq/pqformat.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_sendint(&buf, tupdesc->natts, 2);
for (i = 0; i < tupdesc->natts; ++i)
{
Form_pg_attribute attr = tupdesc->attrs[i];
pq_sendstring(&buf, NameStr(attr->attname));
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, (int) attr->atttypid, 4);
pq_sendint(&buf, attr->attlen, 2);
pq_sendint(&buf, attr->atttypmod, 4);
pq_sendint(&buf, 0, 2); /* 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_sendint(&buf, tupdesc->natts, 2);
for (i = 0; i < tupdesc->natts; ++i)
{
Form_pg_attribute attr = tupdesc->attrs[i];
Datum value;
if (slot->tts_isnull[i])
{
pq_sendint(&buf, -1, 4);
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;
default:
elog(ERROR, "unsupported type OID: %u", attr->atttypid);
}
}
pq_endmessage(&buf);
return true;
}