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

diff --git a/src/backend/access/common/Makefile b/src/backend/access/common/Makefile
index 1fa6de0823a5e8cf3d71052499452f53a1821d2d..d4b8132a9739f430f1acb18934383cd64a68fb1d 100644 (file)
--- a/src/backend/access/common/Makefile
+++ b/src/backend/access/common/Makefile
@@ -12,7 +12,7 @@ subdir = src/backend/access/common
 top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
-OBJS = heaptuple.o indextuple.o printtup.o reloptions.o scankey.o \
-       tupconvert.o tupdesc.o
+OBJS = heaptuple.o indextuple.o printsimple.o printtup.o reloptions.o \
+       scankey.o tupconvert.o tupdesc.o
 
 include $(top_srcdir)/src/backend/common.mk

diff --git a/src/backend/access/common/printsimple.c b/src/backend/access/common/printsimple.c
new file mode 100644 (file)
index 0000000..420de65
--- /dev/null
+++ b/src/backend/access/common/printsimple.c
@@ -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;
+}

diff --git a/src/backend/tcop/dest.c b/src/backend/tcop/dest.c
index da39f43f38c3e7be68d5732faf32486ae7cbb7b0..28081c37654a8787e9423e75c6f768997d6872ca 100644 (file)
--- a/src/backend/tcop/dest.c
+++ b/src/backend/tcop/dest.c
@@ -28,6 +28,7 @@
 
 #include "postgres.h"
 
+#include "access/printsimple.h"
 #include "access/printtup.h"
 #include "access/xact.h"
 #include "commands/copy.h"
@@ -76,6 +77,11 @@ static DestReceiver debugtupDR = {
        DestDebug
 };
 
+static DestReceiver printsimpleDR = {
+       printsimple, printsimple_startup, donothingCleanup, donothingCleanup,
+       DestRemoteSimple
+};
+
 static DestReceiver spi_printtupDR = {
        spi_printtup, spi_dest_startup, donothingCleanup, donothingCleanup,
        DestSPI
@@ -108,6 +114,9 @@ CreateDestReceiver(CommandDest dest)
                case DestRemoteExecute:
                        return printtup_create_DR(dest);
 
+               case DestRemoteSimple:
+                       return &printsimpleDR;
+
                case DestNone:
                        return &donothingDR;
 
@@ -151,6 +160,7 @@ EndCommand(const char *commandTag, CommandDest dest)
        {
                case DestRemote:
                case DestRemoteExecute:
+               case DestRemoteSimple:
 
                        /*
                         * We assume the commandTag is plain ASCII and therefore requires
@@ -191,6 +201,7 @@ NullCommand(CommandDest dest)
        {
                case DestRemote:
                case DestRemoteExecute:
+               case DestRemoteSimple:
 
                        /*
                         * tell the fe that we saw an empty query string.  In protocols
@@ -233,6 +244,7 @@ ReadyForQuery(CommandDest dest)
        {
                case DestRemote:
                case DestRemoteExecute:
+               case DestRemoteSimple:
                        if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
                        {
                                StringInfoData buf;

diff --git a/src/include/access/printsimple.h b/src/include/access/printsimple.h
new file mode 100644 (file)
index 0000000..3f3e7a3
--- /dev/null
+++ b/src/include/access/printsimple.h
@@ -0,0 +1,23 @@
+/*-------------------------------------------------------------------------
+ *
+ * printsimple.h
+ *       print simple tuples without catalog access
+ *
+ * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/printsimple.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef PRINTSIMPLE_H
+#define PRINTSIMPLE_H
+
+#include "tcop/dest.h"
+
+extern bool printsimple(TupleTableSlot *slot, DestReceiver *self);
+extern void printsimple_startup(DestReceiver *self, int operation,
+                                       TupleDesc tupdesc);
+
+#endif   /* PRINTSIMPLE_H */

diff --git a/src/include/tcop/dest.h b/src/include/tcop/dest.h
index 93f9b7463abe2dd8d06a98b19fc287e3b7155c79..c459af2e139ee598b7ee1cc6c64d7b3cf029025a 100644 (file)
--- a/src/include/tcop/dest.h
+++ b/src/include/tcop/dest.h
@@ -89,6 +89,7 @@ typedef enum
        DestDebug,                                      /* results go to debugging output */
        DestRemote,                                     /* results sent to frontend process */
        DestRemoteExecute,                      /* sent to frontend, in Execute command */
+       DestRemoteSimple,                       /* sent to frontend, w/no catalog access */
        DestSPI,                                        /* results sent to SPI manager */
        DestTuplestore,                         /* results sent to Tuplestore */
        DestIntoRel,                            /* results sent to relation (SELECT INTO) */