C++ CreateTupleDescCopy函数代码示例

/**
 * Init nodeDML, which initializes the insert TupleTableSlot.
 * */
DMLState*
ExecInitDML(DML *node, EState *estate, int eflags)
{
	
	/* check for unsupported flags */
	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK | EXEC_FLAG_REWIND)));
	
	DMLState *dmlstate = makeNode(DMLState);
	dmlstate->ps.plan = (Plan *)node;
	dmlstate->ps.state = estate;

	ExecInitResultTupleSlot(estate, &dmlstate->ps);

	dmlstate->ps.targetlist = (List *)
						ExecInitExpr((Expr *) node->plan.targetlist,
						(PlanState *) dmlstate);

	Plan *outerPlan  = outerPlan(node);
	outerPlanState(dmlstate) = ExecInitNode(outerPlan, estate, eflags);

	ExecAssignResultTypeFromTL(&dmlstate->ps);

	/* Create expression evaluation context. This will be used for projections */
	ExecAssignExprContext(estate, &dmlstate->ps);

	/*
	 * Create projection info from the child tuple descriptor and our target list
	 * Projection will be placed in the ResultSlot
	 */
	TupleTableSlot *childResultSlot = outerPlanState(dmlstate)->ps_ResultTupleSlot;
	ExecAssignProjectionInfo(&dmlstate->ps, childResultSlot->tts_tupleDescriptor);
	
	/*
	 * Initialize slot to insert/delete using output relation descriptor.
	 */
	dmlstate->cleanedUpSlot = ExecInitExtraTupleSlot(estate);

	/*
	 * Both input and output of the junk filter include dropped attributes, so
	 * the junk filter doesn't need to do anything special there about them
	 */
	TupleDesc cleanTupType = CreateTupleDescCopy(dmlstate->ps.state->es_result_relation_info->ri_RelationDesc->rd_att); 
	dmlstate->junkfilter = ExecInitJunkFilter(node->plan.targetlist,
			cleanTupType,
			dmlstate->cleanedUpSlot);

	if (estate->es_instrument)
	{
	        dmlstate->ps.cdbexplainbuf = makeStringInfo();

	        /* Request a callback at end of query. */
	        dmlstate->ps.cdbexplainfun = ExecDMLExplainEnd;
	}

	initGpmonPktForDML((Plan *)node, &dmlstate->ps.gpmon_pkt, estate);
	
	return dmlstate;
}

void
CheckerInit(Checker *checker, Relation rel, TupleChecker *tchecker)
{
	TupleDesc	desc;

	checker->tchecker = tchecker;

	/*
	 * When specify ENCODING, we check the input data encoding.
	 * Convert encoding if the client and server encodings are different.
	 */
	checker->db_encoding = GetDatabaseEncoding();
	if (checker->encoding != -1 &&
		(checker->encoding != PG_SQL_ASCII ||
		checker->db_encoding != PG_SQL_ASCII))
		checker->check_encoding = true;

	if (!rel)
		return;

	/* When specify CHECK_CONSTRAINTS, we check the constraints */
	desc = RelationGetDescr(rel);
	if (desc->constr &&
		(checker->check_constraints || desc->constr->has_not_null))
	{
		if (checker->check_constraints)
			checker->has_constraints = true;

		if (desc->constr->has_not_null)
			checker->has_not_null = true;

		checker->resultRelInfo = makeNode(ResultRelInfo);
		checker->resultRelInfo->ri_RangeTableIndex = 1;		/* dummy */
		checker->resultRelInfo->ri_RelationDesc = rel;
		checker->resultRelInfo->ri_TrigDesc = NULL; /* TRIGGER is not supported */
		checker->resultRelInfo->ri_TrigInstrument = NULL;
	}

	if (checker->has_constraints)
	{
		checker->estate = CreateExecutorState();
		checker->estate->es_result_relations = checker->resultRelInfo;
		checker->estate->es_num_result_relations = 1;
		checker->estate->es_result_relation_info = checker->resultRelInfo;

		/* Set up a tuple slot too */
		checker->slot = MakeSingleTupleTableSlot(desc);
	}

	if (!checker->has_constraints && checker->has_not_null)
	{
		int	i;

		checker->desc = CreateTupleDescCopy(desc);
		for (i = 0; i < desc->natts; i++)
			checker->desc->attrs[i]->attnotnull = desc->attrs[i]->attnotnull;
	}
}

/*
 * deflist_to_tuplestore - Helper function to convert DefElem list to
 * tuplestore usable in SRF.
 */
static void
deflist_to_tuplestore(ReturnSetInfo *rsinfo, List *options)
{
	ListCell   *cell;
	TupleDesc	tupdesc;
	Tuplestorestate *tupstore;
	Datum		values[2];
	bool		nulls[2];
	MemoryContext per_query_ctx;
	MemoryContext oldcontext;

	/* check to see if caller supports us returning a tuplestore */
	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that cannot accept a set")));
	if (!(rsinfo->allowedModes & SFRM_Materialize) ||
		rsinfo->expectedDesc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("materialize mode required, but it is not allowed in this context")));

	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
	oldcontext = MemoryContextSwitchTo(per_query_ctx);

	/*
	 * Now prepare the result set.
	 */
	tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);
	tupstore = tuplestore_begin_heap(true, false, work_mem);
	rsinfo->returnMode = SFRM_Materialize;
	rsinfo->setResult = tupstore;
	rsinfo->setDesc = tupdesc;

	foreach(cell, options)
	{
		DefElem    *def = lfirst(cell);

		values[0] = CStringGetTextDatum(def->defname);
		nulls[0] = false;
		if (def->arg)
		{
			values[1] = CStringGetTextDatum(((Value *) (def->arg))->val.str);
			nulls[1] = false;
		}
		else
		{
			values[1] = (Datum) 0;
			nulls[1] = true;
		}
		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
	}

/*
 * RelationNameGetTupleDesc
 *
 * Given a (possibly qualified) relation name, build a TupleDesc.
 *
 * Note: while this works as advertised, it's seldom the best way to
 * build a tupdesc for a function's result type.  It's kept around
 * only for backwards compatibility with existing user-written code.
 */
TupleDesc
RelationNameGetTupleDesc(const char *relname)
{
	RangeVar   *relvar;
	Relation	rel;
	TupleDesc	tupdesc;
	List	   *relname_list;

	/* Open relation and copy the tuple description */
	relname_list = stringToQualifiedNameList(relname);
	relvar = makeRangeVarFromNameList(relname_list);
	rel = relation_openrv(relvar, AccessShareLock);
	tupdesc = CreateTupleDescCopy(RelationGetDescr(rel));
	relation_close(rel, AccessShareLock);

	return tupdesc;
}

Relation
copy_heap(Oid OIDOldHeap)
{
    char NewName[NAMEDATALEN];
    TupleDesc OldHeapDesc, tupdesc;
    Oid OIDNewHeap;
    Relation NewHeap, OldHeap;

    /*
     *  Create a new heap relation with a temporary name, which has the
     *  same tuple description as the old one.
     */
    sprintf(NewName,"temp_%x", OIDOldHeap);

    OldHeap= heap_open(OIDOldHeap);
    OldHeapDesc= RelationGetTupleDescriptor(OldHeap);

    /*
     * Need to make a copy of the tuple descriptor, heap_create modifies
     * it.
     */

    tupdesc = CreateTupleDescCopy(OldHeapDesc);
    
    OIDNewHeap=heap_create(NewName,
			   NULL,
			   OldHeap->rd_rel->relarch,
			   OldHeap->rd_rel->relsmgr,
			   tupdesc);

    if (!OidIsValid(OIDNewHeap))
	elog(WARN,"clusterheap: cannot create temporary heap relation\n");

    NewHeap=heap_open(OIDNewHeap);

    heap_close(NewHeap);
    heap_close(OldHeap);

    return NewHeap;
}

static void
setup_firstcall(FunctionCallInfo fcinfo, FuncCallContext *funcctx, Oid prsid)
{
	TupleDesc	tupdesc;
	MemoryContext oldcontext;
	TypeStorage *st;
	WParserInfo *prs = findprs(prsid);

	oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

	st = (TypeStorage *) palloc(sizeof(TypeStorage));
	st->cur = 0;
	st->list = (LexDescr *) DatumGetPointer(
					OidFunctionCall1(prs->lextype, PointerGetDatum(prs->prs))
		);
	funcctx->user_fctx = (void *) st;
	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
		elog(ERROR, "return type must be a row type");
	tupdesc = CreateTupleDescCopy(tupdesc);
	funcctx->attinmeta = TupleDescGetAttInMetadata(tupdesc);
	MemoryContextSwitchTo(oldcontext);
}

void DMLUtils::PrepareAbstractJoinPlanState(AbstractJoinPlanState *j_plan_state,
                                            const JoinState &j_state) {
  // Copy join type
  j_plan_state->jointype = j_state.jointype;

  // Copy join qual expr states
  j_plan_state->joinqual = CopyExprStateList(j_state.joinqual);

  // Copy ps qual
  j_plan_state->qual = CopyExprStateList(j_state.ps.qual);

  // Copy target list
  j_plan_state->targetlist = CopyExprStateList(j_state.ps.targetlist);

  // Copy tuple desc
  auto tup_desc = j_state.ps.ps_ResultTupleSlot->tts_tupleDescriptor;
  j_plan_state->tts_tupleDescriptor = CreateTupleDescCopy(tup_desc);

  // Construct projection info
  j_plan_state->ps_ProjInfo =
      BuildProjectInfo(j_state.ps.ps_ProjInfo, tup_desc->natts);
}

/*
 * Prepare to receive tuples from executor.
 */
static void
producerStartupReceiver(DestReceiver *self, int operation, TupleDesc typeinfo)
{
	ProducerState *myState = (ProducerState *) self;

	if (ActivePortal)
	{
		/* Normally ExecutorContext is current here. However we should better
		 * create local producer storage in the Portal's context: producer
		 * may keep pushing records to consumers after executor is destroyed.
		 */
		MemoryContext savecontext;
		savecontext = MemoryContextSwitchTo(PortalGetHeapMemory(ActivePortal));
		myState->typeinfo = CreateTupleDescCopy(typeinfo);
		MemoryContextSwitchTo(savecontext);
	}
	else
		myState->typeinfo = typeinfo;

	if (myState->consumer)
		(*myState->consumer->rStartup) (myState->consumer, operation, typeinfo);
}

/*
 * spi_dest_startup
 *		Initialize to receive tuples from Executor into SPITupleTable
 *		of current SPI procedure
 */
void
spi_dest_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
{
	SPITupleTable *tuptable;
	MemoryContext oldcxt;
	MemoryContext tuptabcxt;

	/*
	 * When called by Executor _SPI_curid expected to be equal to
	 * _SPI_connected
	 */
	if (_SPI_curid != _SPI_connected || _SPI_connected < 0)
		elog(ERROR, "improper call to spi_dest_startup");
	if (_SPI_current != &(_SPI_stack[_SPI_curid]))
		elog(ERROR, "SPI stack corrupted");

	if (_SPI_current->tuptable != NULL)
		elog(ERROR, "improper call to spi_dest_startup");

	oldcxt = _SPI_procmem();	/* switch to procedure memory context */

	tuptabcxt = AllocSetContextCreate(CurrentMemoryContext,
									  "SPI TupTable",
									  ALLOCSET_DEFAULT_MINSIZE,
									  ALLOCSET_DEFAULT_INITSIZE,
									  ALLOCSET_DEFAULT_MAXSIZE);
	MemoryContextSwitchTo(tuptabcxt);

	_SPI_current->tuptable = tuptable = (SPITupleTable *)
		palloc(sizeof(SPITupleTable));
	tuptable->tuptabcxt = tuptabcxt;
	tuptable->alloced = tuptable->free = 128;
	tuptable->vals = (HeapTuple *) palloc(tuptable->alloced * sizeof(HeapTuple));
	tuptable->tupdesc = CreateTupleDescCopy(typeinfo);

	MemoryContextSwitchTo(oldcxt);
}

/*
 * PersistHoldablePortal
 *
 * Prepare the specified Portal for access outside of the current
 * transaction. When this function returns, all future accesses to the
 * portal must be done via the Tuplestore (not by invoking the
 * executor).
 */
void
PersistHoldablePortal(Portal portal)
{
	QueryDesc  *queryDesc = PortalGetQueryDesc(portal);
	Portal		saveActivePortal;
	ResourceOwner saveResourceOwner;
	MemoryContext savePortalContext;
	MemoryContext oldcxt;

	/*
	 * If we're preserving a holdable portal, we had better be inside the
	 * transaction that originally created it.
	 */
	Assert(portal->createSubid != InvalidSubTransactionId);
	Assert(queryDesc != NULL);

	/*
	 * Caller must have created the tuplestore already.
	 */
	Assert(portal->holdContext != NULL);
	Assert(portal->holdStore != NULL);

	/*
	 * Before closing down the executor, we must copy the tupdesc into
	 * long-term memory, since it was created in executor memory.
	 */
	oldcxt = MemoryContextSwitchTo(portal->holdContext);

	portal->tupDesc = CreateTupleDescCopy(portal->tupDesc);

	MemoryContextSwitchTo(oldcxt);

	/*
	 * Check for improper portal use, and mark portal active.
	 */
	if (portal->status != PORTAL_READY)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("portal \"%s\" cannot be run", portal->name)));
	portal->status = PORTAL_ACTIVE;

	/*
	 * Set up global portal context pointers.
	 */
	saveActivePortal = ActivePortal;
	saveResourceOwner = CurrentResourceOwner;
	savePortalContext = PortalContext;
	PG_TRY();
	{
		ActivePortal = portal;
		CurrentResourceOwner = portal->resowner;
		PortalContext = PortalGetHeapMemory(portal);

		MemoryContextSwitchTo(PortalContext);

		PushActiveSnapshot(queryDesc->snapshot);

		/*
		 * Rewind the executor: we need to store the entire result set in the
		 * tuplestore, so that subsequent backward FETCHs can be processed.
		 */
		ExecutorRewind(queryDesc);

		/*
		 * Change the destination to output to the tuplestore.	Note we tell
		 * the tuplestore receiver to detoast all data passed through it.
		 */
		queryDesc->dest = CreateDestReceiver(DestTuplestore);
		SetTuplestoreDestReceiverParams(queryDesc->dest,
										portal->holdStore,
										portal->holdContext,
										true);

		/* Fetch the result set into the tuplestore */
		ExecutorRun(queryDesc, ForwardScanDirection, 0L);

		(*queryDesc->dest->rDestroy) (queryDesc->dest);
		queryDesc->dest = NULL;

		/*
		 * Now shut down the inner executor.
		 */
		portal->queryDesc = NULL;		/* prevent double shutdown */
		/* we do not need AfterTriggerEndQuery() here */
		ExecutorEnd(queryDesc);
		FreeQueryDesc(queryDesc);

		/*
		 * Set the position in the result set: ideally, this could be
		 * implemented by just skipping straight to the tuple # that we need
		 * to be at, but the tuplestore API doesn't support that. So we start
		 * at the beginning of the tuplestore and iterate through it until we
//.........这里部分代码省略.........

/*
 * pgstattuple_real
 *
 * The real work occurs here
 */
static Datum
pgstattuple_real(Relation rel, FunctionCallInfo fcinfo)
{
	HeapScanDesc scan;
	HeapTuple	tuple;
	BlockNumber nblocks;
	BlockNumber block = 0;		/* next block to count free space in */
	BlockNumber tupblock;
	Buffer		buffer;
	uint64		table_len;
	uint64		tuple_len = 0;
	uint64		dead_tuple_len = 0;
	uint64		tuple_count = 0;
	uint64		dead_tuple_count = 0;
	double		tuple_percent;
	double		dead_tuple_percent;
	uint64		free_space = 0; /* free/reusable space in bytes */
	double		free_percent;	/* free/reusable space in % */
	TupleDesc	tupdesc;
	AttInMetadata *attinmeta;
	char	  **values;
	int			i;
	Datum		result;

	/* Build a tuple descriptor for our result type */
	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
		elog(ERROR, "return type must be a row type");

	/* make sure we have a persistent copy of the tupdesc */
	tupdesc = CreateTupleDescCopy(tupdesc);

	/*
	 * Generate attribute metadata needed later to produce tuples from raw C
	 * strings
	 */
	attinmeta = TupleDescGetAttInMetadata(tupdesc);

	scan = heap_beginscan(rel, SnapshotAny, 0, NULL);

	nblocks = scan->rs_nblocks; /* # blocks to be scanned */

	/* scan the relation */
	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
	{
		/* must hold a buffer lock to call HeapTupleSatisfiesNow */
		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);

		if (HeapTupleSatisfiesNow(tuple->t_data, scan->rs_cbuf))
		{
			tuple_len += tuple->t_len;
			tuple_count++;
		}
		else
		{
			dead_tuple_len += tuple->t_len;
			dead_tuple_count++;
		}

		LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);

		/*
		 * To avoid physically reading the table twice, try to do the
		 * free-space scan in parallel with the heap scan.	However,
		 * heap_getnext may find no tuples on a given page, so we cannot
		 * simply examine the pages returned by the heap scan.
		 */
		tupblock = BlockIdGetBlockNumber(&tuple->t_self.ip_blkid);

		while (block <= tupblock)
		{
			buffer = ReadBuffer(rel, block);
			LockBuffer(buffer, BUFFER_LOCK_SHARE);
			free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
			LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
			ReleaseBuffer(buffer);
			block++;
		}
	}
	heap_endscan(scan);

	while (block < nblocks)
	{
		buffer = ReadBuffer(rel, block);
		free_space += PageGetFreeSpace((Page) BufferGetPage(buffer));
		ReleaseBuffer(buffer);
		block++;
	}

	heap_close(rel, AccessShareLock);

	table_len = (uint64) nblocks *BLCKSZ;

	if (nblocks == 0)
	{
		tuple_percent = 0.0;
//.........这里部分代码省略.........

/*
 * Initialize a single motion node.  This is called by the executor when a
 * motion node in the plan tree is being initialized.
 *
 * This function is called from:  ExecInitMotion()
 */
void
UpdateMotionLayerNode(MotionLayerState *mlStates, int16 motNodeID, bool preserveOrder, TupleDesc tupDesc, uint64 operatorMemKB)
{
	MemoryContext oldCtxt;
	MotionNodeEntry *pEntry;

	AssertArg(tupDesc != NULL);

	/*
	 * Switch to the Motion Layer's memory-context, so that the motion node
	 * can be reset later.
	 */
	oldCtxt = MemoryContextSwitchTo(mlStates->motion_layer_mctx);
	
	if (motNodeID > mlStates->mneCount)
	{
		AddMotionLayerNode(mlStates, motNodeID);
	}

	pEntry = &mlStates->mnEntries[motNodeID - 1];

	if (!pEntry->valid)
	{
		/*
		 * we'll just set this to 0.  later, ml_ipc will call
		 * setExpectedReceivers() to set this if we are a "Receiving"
		 * motion node.
		 */
		pEntry->num_senders = 0;
	}

	pEntry->motion_node_id = motNodeID;

	pEntry->valid = true;

	/* Finish up initialization of the motion node entry. */
	pEntry->preserve_order = preserveOrder;
	pEntry->tuple_desc = CreateTupleDescCopy(tupDesc);
	InitSerTupInfo(pEntry->tuple_desc, &pEntry->ser_tup_info);

	pEntry->memKB = operatorMemKB;

	if (!preserveOrder)
	{
		Assert(pEntry->memKB > 0);
		
		/* Create a tuple-store for the motion node's incoming tuples. */
		pEntry->ready_tuples = htfifo_create(pEntry->memKB);
	}
	else
		pEntry->ready_tuples = NULL;


	pEntry->num_stream_ends_recvd = 0;

	/* Initialize statistics counters. */
	pEntry->stat_total_chunks_sent = 0;
	pEntry->stat_total_bytes_sent = 0;
	pEntry->stat_tuple_bytes_sent = 0;
	pEntry->stat_total_sends = 0;
	pEntry->stat_total_recvs = 0;
	pEntry->stat_tuples_available = 0;
	pEntry->stat_tuples_available_hwm = 0;
	pEntry->stat_total_chunks_recvd = 0;
	pEntry->stat_total_bytes_recvd = 0;
	pEntry->stat_tuple_bytes_recvd = 0;
	pEntry->sel_rd_wait = 0;
	pEntry->sel_wr_wait = 0;

	pEntry->cleanedUp = false;
	pEntry->stopped = false;
	pEntry->moreNetWork = true;


	/* All done!  Go back to caller memory-context. */
	MemoryContextSwitchTo(oldCtxt);
}

static inline Datum
each_worker(PG_FUNCTION_ARGS, bool as_text)
{
	text	   *json = PG_GETARG_TEXT_P(0);
	JsonLexContext *lex = makeJsonLexContext(json, true);
	JsonSemAction sem;
	ReturnSetInfo *rsi;
	MemoryContext old_cxt;
	TupleDesc	tupdesc;
	EachState	state;

	state = palloc0(sizeof(eachState));
	sem = palloc0(sizeof(jsonSemAction));

	rsi = (ReturnSetInfo *) fcinfo->resultinfo;

	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
		(rsi->allowedModes & SFRM_Materialize) == 0 ||
		rsi->expectedDesc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that "
						"cannot accept a set")));


	rsi->returnMode = SFRM_Materialize;

	(void) get_call_result_type(fcinfo, NULL, &tupdesc);

	/* make these in a sufficiently long-lived memory context */
	old_cxt = MemoryContextSwitchTo(rsi->econtext->ecxt_per_query_memory);

	state->ret_tdesc = CreateTupleDescCopy(tupdesc);
	BlessTupleDesc(state->ret_tdesc);
	state->tuple_store =
		tuplestore_begin_heap(rsi->allowedModes & SFRM_Materialize,
							  false, work_mem);

	MemoryContextSwitchTo(old_cxt);

	sem->semstate = (void *) state;
	sem->array_start = each_array_start;
	sem->scalar = each_scalar;
	sem->object_field_start = each_object_field_start;
	sem->object_field_end = each_object_field_end;

	state->normalize_results = as_text;
	state->next_scalar = false;

	state->lex = lex;
	state->tmp_cxt = AllocSetContextCreate(CurrentMemoryContext,
										   "json_each temporary cxt",
										   ALLOCSET_DEFAULT_MINSIZE,
										   ALLOCSET_DEFAULT_INITSIZE,
										   ALLOCSET_DEFAULT_MAXSIZE);

	pg_parse_json(lex, sem);

	rsi->setResult = state->tuple_store;
	rsi->setDesc = state->ret_tdesc;

	PG_RETURN_NULL();
}

/*
 * SQL function json_populate_recordset
 *
 * set fields in a set of records from the argument json,
 * which must be an array of objects.
 *
 * similar to json_populate_record, but the tuple-building code
 * is pushed down into the semantic action handlers so it's done
 * per object in the array.
 */
Datum
json_populate_recordset(PG_FUNCTION_ARGS)
{
	Oid			argtype = get_fn_expr_argtype(fcinfo->flinfo, 0);
	text	   *json = PG_GETARG_TEXT_P(1);
	bool		use_json_as_text = PG_GETARG_BOOL(2);
	ReturnSetInfo *rsi;
	MemoryContext old_cxt;
	Oid			tupType;
	int32		tupTypmod;
	HeapTupleHeader rec;
	TupleDesc	tupdesc;
	RecordIOData *my_extra;
	int			ncolumns;
	JsonLexContext *lex;
	JsonSemAction sem;
	PopulateRecordsetState state;

	if (!type_is_rowtype(argtype))
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("first argument must be a rowtype")));

	rsi = (ReturnSetInfo *) fcinfo->resultinfo;

	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
		(rsi->allowedModes & SFRM_Materialize) == 0 ||
		rsi->expectedDesc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that "
						"cannot accept a set")));


	rsi->returnMode = SFRM_Materialize;

	/*
	 * get the tupdesc from the result set info - it must be a record type
	 * because we already checked that arg1 is a record type.
	 */
	(void) get_call_result_type(fcinfo, NULL, &tupdesc);

	state = palloc0(sizeof(populateRecordsetState));
	sem = palloc0(sizeof(jsonSemAction));


	/* make these in a sufficiently long-lived memory context */
	old_cxt = MemoryContextSwitchTo(rsi->econtext->ecxt_per_query_memory);

	state->ret_tdesc = CreateTupleDescCopy(tupdesc);
	BlessTupleDesc(state->ret_tdesc);
	state->tuple_store =
		tuplestore_begin_heap(rsi->allowedModes & SFRM_Materialize,
							  false, work_mem);

	MemoryContextSwitchTo(old_cxt);

	/* if the json is null send back an empty set */
	if (PG_ARGISNULL(1))
		PG_RETURN_NULL();

	if (PG_ARGISNULL(0))
		rec = NULL;
	else
		rec = PG_GETARG_HEAPTUPLEHEADER(0);

	tupType = tupdesc->tdtypeid;
	tupTypmod = tupdesc->tdtypmod;
	ncolumns = tupdesc->natts;

	lex = makeJsonLexContext(json, true);

	/*
	 * We arrange to look up the needed I/O info just once per series of
	 * calls, assuming the record type doesn't change underneath us.
	 */
	my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
	if (my_extra == NULL ||
		my_extra->ncolumns != ncolumns)
	{
		fcinfo->flinfo->fn_extra =
			MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
							   sizeof(RecordIOData) - sizeof(ColumnIOData)
							   + ncolumns * sizeof(ColumnIOData));
		my_extra = (RecordIOData *) fcinfo->flinfo->fn_extra;
		my_extra->record_type = InvalidOid;
		my_extra->record_typmod = 0;
	}

	if (my_extra->record_type != tupType ||
//.........这里部分代码省略.........

Datum
xpath_table(PG_FUNCTION_ARGS)
{
	/* Function parameters */
	char	   *pkeyfield = text_to_cstring(PG_GETARG_TEXT_PP(0));
	char	   *xmlfield = text_to_cstring(PG_GETARG_TEXT_PP(1));
	char	   *relname = text_to_cstring(PG_GETARG_TEXT_PP(2));
	char	   *xpathset = text_to_cstring(PG_GETARG_TEXT_PP(3));
	char	   *condition = text_to_cstring(PG_GETARG_TEXT_PP(4));

	/* SPI (input tuple) support */
	SPITupleTable *tuptable;
	HeapTuple	spi_tuple;
	TupleDesc	spi_tupdesc;

	/* Output tuple (tuplestore) support */
	Tuplestorestate *tupstore = NULL;
	TupleDesc	ret_tupdesc;
	HeapTuple	ret_tuple;

	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
	AttInMetadata *attinmeta;
	MemoryContext per_query_ctx;
	MemoryContext oldcontext;

	char	  **values;
	xmlChar   **xpaths;
	char	   *pos;
	const char *pathsep = "|";

	int			numpaths;
	int			ret;
	int			proc;
	int			i;
	int			j;
	int			rownr;			/* For issuing multiple rows from one original
								 * document */
	bool		had_values;		/* To determine end of nodeset results */
	StringInfoData query_buf;
	PgXmlErrorContext *xmlerrcxt;
	volatile xmlDocPtr doctree = NULL;

	/* We only have a valid tuple description in table function mode */
	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that cannot accept a set")));
	if (rsinfo->expectedDesc == NULL)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("xpath_table must be called as a table function")));

	/*
	 * We want to materialise because it means that we don't have to carry
	 * libxml2 parser state between invocations of this function
	 */
	if (!(rsinfo->allowedModes & SFRM_Materialize))
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
			   errmsg("xpath_table requires Materialize mode, but it is not "
					  "allowed in this context")));

	/*
	 * The tuplestore must exist in a higher context than this function call
	 * (per_query_ctx is used)
	 */
	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
	oldcontext = MemoryContextSwitchTo(per_query_ctx);

	/*
	 * Create the tuplestore - work_mem is the max in-memory size before a
	 * file is created on disk to hold it.
	 */
	tupstore =
		tuplestore_begin_heap(rsinfo->allowedModes & SFRM_Materialize_Random,
							  false, work_mem);

	MemoryContextSwitchTo(oldcontext);

	/* get the requested return tuple description */
	ret_tupdesc = CreateTupleDescCopy(rsinfo->expectedDesc);

	/* must have at least one output column (for the pkey) */
	if (ret_tupdesc->natts < 1)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("xpath_table must have at least one output column")));

	/*
	 * At the moment we assume that the returned attributes make sense for the
	 * XPath specififed (i.e. we trust the caller). It's not fatal if they get
	 * it wrong - the input function for the column type will raise an error
	 * if the path result can't be converted into the correct binary
	 * representation.
	 */

	attinmeta = TupleDescGetAttInMetadata(ret_tupdesc);

	/* Set return mode and allocate value space. */
	rsinfo->returnMode = SFRM_Materialize;
//.........这里部分代码省略.........