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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
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110
src/backend/access/common/printsimple.c
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110
src/backend/access/common/printsimple.c
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/*-------------------------------------------------------------------------
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*
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* printsimple.c
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* Routines to print out tuples containing only a limited range of
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* builtin types without catalog access. This is intended for
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* backends that don't have catalog access because they are not bound
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* to a specific database, such as some walsender processes. It
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* doesn't handle standalone backends or protocol versions other than
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* 3.0, because we don't need such handling for current applications.
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/backend/access/common/printsimple.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/printsimple.h"
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#include "catalog/pg_type.h"
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#include "fmgr.h"
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#include "libpq/pqformat.h"
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/*
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* At startup time, send a RowDescription message.
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*/
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void
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printsimple_startup(DestReceiver *self, int operation, TupleDesc tupdesc)
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{
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StringInfoData buf;
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int i;
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pq_beginmessage(&buf, 'T'); /* RowDescription */
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pq_sendint(&buf, tupdesc->natts, 2);
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for (i = 0; i < tupdesc->natts; ++i)
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{
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Form_pg_attribute attr = tupdesc->attrs[i];
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pq_sendstring(&buf, NameStr(attr->attname));
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pq_sendint(&buf, 0, 4); /* table oid */
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pq_sendint(&buf, 0, 2); /* attnum */
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pq_sendint(&buf, (int) attr->atttypid, 4);
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pq_sendint(&buf, attr->attlen, 2);
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pq_sendint(&buf, attr->atttypmod, 4);
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pq_sendint(&buf, 0, 2); /* format code */
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}
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pq_endmessage(&buf);
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}
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/*
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* For each tuple, send a DataRow message.
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*/
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bool
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printsimple(TupleTableSlot *slot, DestReceiver *self)
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{
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TupleDesc tupdesc = slot->tts_tupleDescriptor;
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StringInfoData buf;
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int i;
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/* Make sure the tuple is fully deconstructed */
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slot_getallattrs(slot);
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/* Prepare and send message */
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pq_beginmessage(&buf, 'D');
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pq_sendint(&buf, tupdesc->natts, 2);
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for (i = 0; i < tupdesc->natts; ++i)
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{
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Form_pg_attribute attr = tupdesc->attrs[i];
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Datum value;
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if (slot->tts_isnull[i])
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{
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pq_sendint(&buf, -1, 4);
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continue;
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}
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value = slot->tts_values[i];
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/*
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* We can't call the regular type output functions here because we
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* might not have catalog access. Instead, we must hard-wire
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* knowledge of the required types.
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*/
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switch (attr->atttypid)
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{
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case TEXTOID:
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{
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text *t = DatumGetTextPP(value);
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pq_sendcountedtext(&buf,
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VARDATA_ANY(t),
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VARSIZE_ANY_EXHDR(t),
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false);
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}
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break;
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default:
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elog(ERROR, "unsupported type OID: %u", attr->atttypid);
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}
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}
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pq_endmessage(&buf);
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return true;
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}
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