Create explain_dr.c and move DestReceiver-related code there.

explain.c has grown rather large, and the code that deals with the
DestReceiver that supports the SERIALIZE option is pretty easily severable
from the rest of explain.c; hence, move it to a separate file.

Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: http://postgr.es/m/CA+TgmoYutMw1Jgo8BWUmB3TqnOhsEAJiYO=rOQufF4gPLWmkLQ@mail.gmail.com

Author: robertmhaas

src/backend/commands/Makefile

@@ -34,6 +34,7 @@ OBJS = \
 	dropcmds.o \
 	event_trigger.o \
 	explain.o \
+	explain_dr.o \
 	explain_format.o \
 	extension.o \
 	foreigncmds.o \

src/backend/commands/explain.c

@@ -17,6 +17,7 @@
 #include "catalog/pg_type.h"
 #include "commands/createas.h"
 #include "commands/defrem.h"
+#include "commands/explain_dr.h"
 #include "commands/explain_format.h"
 #include "commands/prepare.h"
 #include "foreign/fdwapi.h"
@@ -50,14 +51,6 @@ ExplainOneQuery_hook_type ExplainOneQuery_hook = NULL;
 explain_get_index_name_hook_type explain_get_index_name_hook = NULL;
 
 
-/* Instrumentation data for SERIALIZE option */
-typedef struct SerializeMetrics
-{
-	uint64		bytesSent;		/* # of bytes serialized */
-	instr_time	timeSpent;		/* time spent serializing */
-	BufferUsage bufferUsage;	/* buffers accessed during serialization */
-} SerializeMetrics;
-
 /*
  * Various places within need to convert bytes to kilobytes.  Round these up
  * to the next whole kilobyte.
@@ -161,7 +154,6 @@ static ExplainWorkersState *ExplainCreateWorkersState(int num_workers);
 static void ExplainOpenWorker(int n, ExplainState *es);
 static void ExplainCloseWorker(int n, ExplainState *es);
 static void ExplainFlushWorkersState(ExplainState *es);
-static SerializeMetrics GetSerializationMetrics(DestReceiver *dest);
 
 
 
@@ -4939,292 +4931,3 @@ ExplainFlushWorkersState(ExplainState *es)
 	pfree(wstate->worker_state_save);
 	pfree(wstate);
 }
-
-/*
- * DestReceiver functions for SERIALIZE option
- *
- * A DestReceiver for query tuples, that serializes passed rows into RowData
- * messages while measuring the resources expended and total serialized size,
- * while never sending the data to the client.  This allows measuring the
- * overhead of deTOASTing and datatype out/sendfuncs, which are not otherwise
- * exercisable without actually hitting the network.
- */
-typedef struct SerializeDestReceiver
-{
-	DestReceiver pub;
-	ExplainState *es;			/* this EXPLAIN statement's ExplainState */
-	int8		format;			/* text or binary, like pq wire protocol */
-	TupleDesc	attrinfo;		/* the output tuple desc */
-	int			nattrs;			/* current number of columns */
-	FmgrInfo   *finfos;			/* precomputed call info for output fns */
-	MemoryContext tmpcontext;	/* per-row temporary memory context */
-	StringInfoData buf;			/* buffer to hold the constructed message */
-	SerializeMetrics metrics;	/* collected metrics */
-} SerializeDestReceiver;
-
-/*
- * Get the function lookup info that we'll need for output.
- *
- * This is a subset of what printtup_prepare_info() does.  We don't need to
- * cope with format choices varying across columns, so it's slightly simpler.
- */
-static void
-serialize_prepare_info(SerializeDestReceiver *receiver,
-					   TupleDesc typeinfo, int nattrs)
-{
-	/* get rid of any old data */
-	if (receiver->finfos)
-		pfree(receiver->finfos);
-	receiver->finfos = NULL;
-
-	receiver->attrinfo = typeinfo;
-	receiver->nattrs = nattrs;
-	if (nattrs <= 0)
-		return;
-
-	receiver->finfos = (FmgrInfo *) palloc0(nattrs * sizeof(FmgrInfo));
-
-	for (int i = 0; i < nattrs; i++)
-	{
-		FmgrInfo   *finfo = receiver->finfos + i;
-		Form_pg_attribute attr = TupleDescAttr(typeinfo, i);
-		Oid			typoutput;
-		Oid			typsend;
-		bool		typisvarlena;
-
-		if (receiver->format == 0)
-		{
-			/* wire protocol format text */
-			getTypeOutputInfo(attr->atttypid,
-							  &typoutput,
-							  &typisvarlena);
-			fmgr_info(typoutput, finfo);
-		}
-		else if (receiver->format == 1)
-		{
-			/* wire protocol format binary */
-			getTypeBinaryOutputInfo(attr->atttypid,
-									&typsend,
-									&typisvarlena);
-			fmgr_info(typsend, finfo);
-		}
-		else
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("unsupported format code: %d", receiver->format)));
-	}
-}
-
-/*
- * serializeAnalyzeReceive - collect tuples for EXPLAIN (SERIALIZE)
- *
- * This should match printtup() in printtup.c as closely as possible,
- * except for the addition of measurement code.
- */
-static bool
-serializeAnalyzeReceive(TupleTableSlot *slot, DestReceiver *self)
-{
-	TupleDesc	typeinfo = slot->tts_tupleDescriptor;
-	SerializeDestReceiver *myState = (SerializeDestReceiver *) self;
-	MemoryContext oldcontext;
-	StringInfo	buf = &myState->buf;
-	int			natts = typeinfo->natts;
-	instr_time	start,
-				end;
-	BufferUsage instr_start;
-
-	/* only measure time, buffers if requested */
-	if (myState->es->timing)
-		INSTR_TIME_SET_CURRENT(start);
-	if (myState->es->buffers)
-		instr_start = pgBufferUsage;
-
-	/* Set or update my derived attribute info, if needed */
-	if (myState->attrinfo != typeinfo || myState->nattrs != natts)
-		serialize_prepare_info(myState, typeinfo, natts);
-
-	/* Make sure the tuple is fully deconstructed */
-	slot_getallattrs(slot);
-
-	/* Switch into per-row context so we can recover memory below */
-	oldcontext = MemoryContextSwitchTo(myState->tmpcontext);
-
-	/*
-	 * Prepare a DataRow message (note buffer is in per-query context)
-	 *
-	 * Note that we fill a StringInfo buffer the same as printtup() does, so
-	 * as to capture the costs of manipulating the strings accurately.
-	 */
-	pq_beginmessage_reuse(buf, PqMsg_DataRow);
-
-	pq_sendint16(buf, natts);
-
-	/*
-	 * send the attributes of this tuple
-	 */
-	for (int i = 0; i < natts; i++)
-	{
-		FmgrInfo   *finfo = myState->finfos + i;
-		Datum		attr = slot->tts_values[i];
-
-		if (slot->tts_isnull[i])
-		{
-			pq_sendint32(buf, -1);
-			continue;
-		}
-
-		if (myState->format == 0)
-		{
-			/* Text output */
-			char	   *outputstr;
-
-			outputstr = OutputFunctionCall(finfo, attr);
-			pq_sendcountedtext(buf, outputstr, strlen(outputstr));
-		}
-		else
-		{
-			/* Binary output */
-			bytea	   *outputbytes;
-
-			outputbytes = SendFunctionCall(finfo, attr);
-			pq_sendint32(buf, VARSIZE(outputbytes) - VARHDRSZ);
-			pq_sendbytes(buf, VARDATA(outputbytes),
-						 VARSIZE(outputbytes) - VARHDRSZ);
-		}
-	}
-
-	/*
-	 * We mustn't call pq_endmessage_reuse(), since that would actually send
-	 * the data to the client.  Just count the data, instead.  We can leave
-	 * the buffer alone; it'll be reset on the next iteration (as would also
-	 * happen in printtup()).
-	 */
-	myState->metrics.bytesSent += buf->len;
-
-	/* Return to caller's context, and flush row's temporary memory */
-	MemoryContextSwitchTo(oldcontext);
-	MemoryContextReset(myState->tmpcontext);
-
-	/* Update timing data */
-	if (myState->es->timing)
-	{
-		INSTR_TIME_SET_CURRENT(end);
-		INSTR_TIME_ACCUM_DIFF(myState->metrics.timeSpent, end, start);
-	}
-
-	/* Update buffer metrics */
-	if (myState->es->buffers)
-		BufferUsageAccumDiff(&myState->metrics.bufferUsage,
-							 &pgBufferUsage,
-							 &instr_start);
-
-	return true;
-}
-
-/*
- * serializeAnalyzeStartup - start up the serializeAnalyze receiver
- */
-static void
-serializeAnalyzeStartup(DestReceiver *self, int operation, TupleDesc typeinfo)
-{
-	SerializeDestReceiver *receiver = (SerializeDestReceiver *) self;
-
-	Assert(receiver->es != NULL);
-
-	switch (receiver->es->serialize)
-	{
-		case EXPLAIN_SERIALIZE_NONE:
-			Assert(false);
-			break;
-		case EXPLAIN_SERIALIZE_TEXT:
-			receiver->format = 0;	/* wire protocol format text */
-			break;
-		case EXPLAIN_SERIALIZE_BINARY:
-			receiver->format = 1;	/* wire protocol format binary */
-			break;
-	}
-
-	/* Create per-row temporary memory context */
-	receiver->tmpcontext = AllocSetContextCreate(CurrentMemoryContext,
-												 "SerializeTupleReceive",
-												 ALLOCSET_DEFAULT_SIZES);
-
-	/* The output buffer is re-used across rows, as in printtup.c */
-	initStringInfo(&receiver->buf);
-
-	/* Initialize results counters */
-	memset(&receiver->metrics, 0, sizeof(SerializeMetrics));
-	INSTR_TIME_SET_ZERO(receiver->metrics.timeSpent);
-}
-
-/*
- * serializeAnalyzeShutdown - shut down the serializeAnalyze receiver
- */
-static void
-serializeAnalyzeShutdown(DestReceiver *self)
-{
-	SerializeDestReceiver *receiver = (SerializeDestReceiver *) self;
-
-	if (receiver->finfos)
-		pfree(receiver->finfos);
-	receiver->finfos = NULL;
-
-	if (receiver->buf.data)
-		pfree(receiver->buf.data);
-	receiver->buf.data = NULL;
-
-	if (receiver->tmpcontext)
-		MemoryContextDelete(receiver->tmpcontext);
-	receiver->tmpcontext = NULL;
-}
-
-/*
- * serializeAnalyzeDestroy - destroy the serializeAnalyze receiver
- */
-static void
-serializeAnalyzeDestroy(DestReceiver *self)
-{
-	pfree(self);
-}
-
-/*
- * Build a DestReceiver for EXPLAIN (SERIALIZE) instrumentation.
- */
-DestReceiver *
-CreateExplainSerializeDestReceiver(ExplainState *es)
-{
-	SerializeDestReceiver *self;
-
-	self = (SerializeDestReceiver *) palloc0(sizeof(SerializeDestReceiver));
-
-	self->pub.receiveSlot = serializeAnalyzeReceive;
-	self->pub.rStartup = serializeAnalyzeStartup;
-	self->pub.rShutdown = serializeAnalyzeShutdown;
-	self->pub.rDestroy = serializeAnalyzeDestroy;
-	self->pub.mydest = DestExplainSerialize;
-
-	self->es = es;
-
-	return (DestReceiver *) self;
-}
-
-/*
- * GetSerializationMetrics - collect metrics
- *
- * We have to be careful here since the receiver could be an IntoRel
- * receiver if the subject statement is CREATE TABLE AS.  In that
- * case, return all-zeroes stats.
- */
-static SerializeMetrics
-GetSerializationMetrics(DestReceiver *dest)
-{
-	SerializeMetrics empty;
-
-	if (dest->mydest == DestExplainSerialize)
-		return ((SerializeDestReceiver *) dest)->metrics;
-
-	memset(&empty, 0, sizeof(SerializeMetrics));
-	INSTR_TIME_SET_ZERO(empty.timeSpent);
-
-	return empty;
-}