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232 lines
5.5 KiB
C
232 lines
5.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* dest.c
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* support for communication destinations
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*
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*
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* Portions Copyright (c) 1996-2005, 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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* $PostgreSQL: pgsql/src/backend/tcop/dest.c,v 1.66 2005/10/15 02:49:26 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* INTERFACE ROUTINES
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* BeginCommand - initialize the destination at start of command
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* CreateDestReceiver - create tuple receiver object for destination
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* EndCommand - clean up the destination at end of command
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* NullCommand - tell dest that an empty query string was recognized
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* ReadyForQuery - tell dest that we are ready for a new query
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*
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* NOTES
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* These routines do the appropriate work before and after
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* tuples are returned by a query to keep the backend and the
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* "destination" portals synchronized.
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*/
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#include "postgres.h"
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#include "access/printtup.h"
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#include "access/xact.h"
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#include "executor/tstoreReceiver.h"
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#include "libpq/libpq.h"
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#include "libpq/pqformat.h"
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#include "utils/portal.h"
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/* ----------------
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* dummy DestReceiver functions
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* ----------------
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*/
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static void
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donothingReceive(TupleTableSlot *slot, DestReceiver *self)
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{
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}
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static void
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donothingStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
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{
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}
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static void
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donothingCleanup(DestReceiver *self)
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{
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/* this is used for both shutdown and destroy methods */
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}
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/* ----------------
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* static DestReceiver structs for dest types needing no local state
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* ----------------
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*/
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static DestReceiver donothingDR = {
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donothingReceive, donothingStartup, donothingCleanup, donothingCleanup,
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None
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};
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static DestReceiver debugtupDR = {
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debugtup, debugStartup, donothingCleanup, donothingCleanup,
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Debug
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};
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static DestReceiver spi_printtupDR = {
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spi_printtup, spi_dest_startup, donothingCleanup, donothingCleanup,
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SPI
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};
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/* Globally available receiver for None */
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DestReceiver *None_Receiver = &donothingDR;
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/* ----------------
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* BeginCommand - initialize the destination at start of command
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* ----------------
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*/
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void
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BeginCommand(const char *commandTag, CommandDest dest)
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{
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/* Nothing to do at present */
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}
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/* ----------------
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* CreateDestReceiver - return appropriate receiver function set for dest
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*
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* Note: a Portal must be specified for destinations Remote, RemoteExecute,
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* and Tuplestore. It can be NULL for the others.
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* ----------------
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*/
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DestReceiver *
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CreateDestReceiver(CommandDest dest, Portal portal)
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{
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switch (dest)
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{
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case Remote:
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case RemoteExecute:
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if (portal == NULL)
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elog(ERROR, "no portal specified for Remote receiver");
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return printtup_create_DR(dest, portal);
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case None:
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return &donothingDR;
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case Debug:
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return &debugtupDR;
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case SPI:
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return &spi_printtupDR;
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case Tuplestore:
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if (portal == NULL)
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elog(ERROR, "no portal specified for Tuplestore receiver");
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if (portal->holdStore == NULL ||
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portal->holdContext == NULL)
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elog(ERROR, "portal has no holdStore");
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return CreateTuplestoreDestReceiver(portal->holdStore,
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portal->holdContext);
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}
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/* should never get here */
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return &donothingDR;
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}
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/* ----------------
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* EndCommand - clean up the destination at end of command
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* ----------------
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*/
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void
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EndCommand(const char *commandTag, CommandDest dest)
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{
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switch (dest)
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{
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case Remote:
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case RemoteExecute:
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pq_puttextmessage('C', commandTag);
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break;
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case None:
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case Debug:
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case SPI:
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case Tuplestore:
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break;
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}
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}
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/* ----------------
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* NullCommand - tell dest that an empty query string was recognized
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*
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* In FE/BE protocol version 1.0, this hack is necessary to support
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* libpq's crufty way of determining whether a multiple-command
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* query string is done. In protocol 2.0 it's probably not really
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* necessary to distinguish empty queries anymore, but we still do it
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* for backwards compatibility with 1.0. In protocol 3.0 it has some
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* use again, since it ensures that there will be a recognizable end
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* to the response to an Execute message.
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* ----------------
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*/
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void
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NullCommand(CommandDest dest)
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{
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switch (dest)
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{
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case Remote:
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case RemoteExecute:
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/*
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* tell the fe that we saw an empty query string. In protocols
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* before 3.0 this has a useless empty-string message body.
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*/
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if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
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pq_putemptymessage('I');
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else
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pq_puttextmessage('I', "");
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break;
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case None:
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case Debug:
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case SPI:
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case Tuplestore:
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break;
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}
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}
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/* ----------------
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* ReadyForQuery - tell dest that we are ready for a new query
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*
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* The ReadyForQuery message is sent in protocol versions 2.0 and up
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* so that the FE can tell when we are done processing a query string.
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* In versions 3.0 and up, it also carries a transaction state indicator.
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*
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* Note that by flushing the stdio buffer here, we can avoid doing it
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* most other places and thus reduce the number of separate packets sent.
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* ----------------
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*/
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void
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ReadyForQuery(CommandDest dest)
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{
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switch (dest)
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{
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case Remote:
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case RemoteExecute:
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if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
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{
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StringInfoData buf;
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pq_beginmessage(&buf, 'Z');
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pq_sendbyte(&buf, TransactionBlockStatusCode());
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pq_endmessage(&buf);
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}
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else if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
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pq_putemptymessage('Z');
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/* Flush output at end of cycle in any case. */
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pq_flush();
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break;
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case None:
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case Debug:
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case SPI:
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case Tuplestore:
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break;
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}
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}
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