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Improve performance of SendRowDescriptionMessage.

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There's three categories of changes leading to better performance:
- Splitting the per-attribute part of SendRowDescriptionMessage into a
  v2 and a v3 version allows avoiding branches for every attribute.
- Preallocating the size of the buffer to be big enough for all
  attributes and then using pq_write* avoids unnecessary buffer
  size checks & resizing.
- Reusing a persistently allocated StringInfo for all
  SendRowDescriptionMessage() invocations avoids repeated allocations
  & reallocations.

Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
This commit is contained in:
Andres Freund
2017-10-11 16:49:31 -07:00
parent cff440d368
commit 4c119fbcd4
3 changed files with 140 additions and 49 deletions
Download Patch File Download Diff File Expand all files Collapse all files

150
src/backend/access/common/printtup.c
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@ -32,6 +32,10 @@ static bool printtup_internal_20(TupleTableSlot *slot, DestReceiver *self);
static void printtup_shutdown(DestReceiver *self);
static void printtup_destroy(DestReceiver *self);
static void SendRowDescriptionCols_2(StringInfo buf, TupleDesc typeinfo,
List *targetlist, int16 *formats);
static void SendRowDescriptionCols_3(StringInfo buf, TupleDesc typeinfo,
List *targetlist, int16 *formats);
/* ----------------------------------------------------------------
* printtup / debugtup support
@ -161,7 +165,8 @@ printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
* descriptor of the tuples.
*/
if (myState->sendDescrip)
SendRowDescriptionMessage(typeinfo,
SendRowDescriptionMessage(&myState->buf,
typeinfo,
FetchPortalTargetList(portal),
portal->formats);
@ -189,16 +194,109 @@ printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
* send zeroes for the format codes in that case.
*/
void
SendRowDescriptionMessage(TupleDesc typeinfo, List *targetlist, int16 *formats)
SendRowDescriptionMessage(StringInfo buf, TupleDesc typeinfo,
List *targetlist, int16 *formats)
{
int natts = typeinfo->natts;
int proto = PG_PROTOCOL_MAJOR(FrontendProtocol);
/* tuple descriptor message type */
pq_beginmessage_reuse(buf, 'T');
/* # of attrs in tuples */
pq_sendint16(buf, natts);
if (proto >= 3)
SendRowDescriptionCols_3(buf, typeinfo, targetlist, formats);
else
SendRowDescriptionCols_2(buf, typeinfo, targetlist, formats);
pq_endmessage_reuse(buf);
}
/*
* Send description for each column when using v3+ protocol
*/
static void
SendRowDescriptionCols_3(StringInfo buf, TupleDesc typeinfo, List *targetlist, int16 *formats)
{
int natts = typeinfo->natts;
int i;
StringInfoData buf;
ListCell *tlist_item = list_head(targetlist);
pq_beginmessage(&buf, 'T'); /* tuple descriptor message type */
pq_sendint(&buf, natts, 2); /* # of attrs in tuples */
/*
* Preallocate memory for the entire message to be sent. That allows to
* use the significantly faster inline pqformat.h functions and to avoid
* reallocations.
*
* Have to overestimate the size of the column-names, to account for
* character set overhead.
*/
enlargeStringInfo(buf, (NAMEDATALEN * MAX_CONVERSION_GROWTH /* attname */
+ sizeof(Oid) /* resorigtbl */
+ sizeof(AttrNumber) /* resorigcol */
+ sizeof(Oid) /* atttypid */
+ sizeof(int16) /* attlen */
+ sizeof(int32) /* attypmod */
+ sizeof(int16) /* format */
) * natts);
for (i = 0; i < natts; ++i)
{
Form_pg_attribute att = TupleDescAttr(typeinfo, i);
Oid atttypid = att->atttypid;
int32 atttypmod = att->atttypmod;
Oid resorigtbl;
AttrNumber resorigcol;
int16 format;
/*
* If column is a domain, send the base type and typmod instead.
* Lookup before sending any ints, for efficiency.
*/
atttypid = getBaseTypeAndTypmod(atttypid, &atttypmod);
/* Do we have a non-resjunk tlist item? */
while (tlist_item &&
((TargetEntry *) lfirst(tlist_item))->resjunk)
tlist_item = lnext(tlist_item);
if (tlist_item)
{
TargetEntry *tle = (TargetEntry *) lfirst(tlist_item);
resorigtbl = tle->resorigtbl;
resorigcol = tle->resorigcol;
tlist_item = lnext(tlist_item);
}
else
{
/* No info available, so send zeroes */
resorigtbl = 0;
resorigcol = 0;
}
if (formats)
format = formats[i];
else
format = 0;
pq_writestring(buf, NameStr(att->attname));
pq_writeint32(buf, resorigtbl);
pq_writeint16(buf, resorigcol);
pq_writeint32(buf, atttypid);
pq_writeint16(buf, att->attlen);
pq_writeint32(buf, atttypmod);
pq_writeint16(buf, format);
}
}
/*
* Send description for each column when using v2 protocol
*/
static void
SendRowDescriptionCols_2(StringInfo buf, TupleDesc typeinfo, List *targetlist, int16 *formats)
{
int natts = typeinfo->natts;
int i;
for (i = 0; i < natts; ++i)
{
@ -206,44 +304,16 @@ SendRowDescriptionMessage(TupleDesc typeinfo, List *targetlist, int16 *formats)
Oid atttypid = att->atttypid;
int32 atttypmod = att->atttypmod;
pq_sendstring(&buf, NameStr(att->attname));
/* column ID info appears in protocol 3.0 and up */
if (proto >= 3)
{
/* Do we have a non-resjunk tlist item? */
while (tlist_item &&
((TargetEntry *) lfirst(tlist_item))->resjunk)
tlist_item = lnext(tlist_item);
if (tlist_item)
{
TargetEntry *tle = (TargetEntry *) lfirst(tlist_item);
pq_sendint(&buf, tle->resorigtbl, 4);
pq_sendint(&buf, tle->resorigcol, 2);
tlist_item = lnext(tlist_item);
}
else
{
/* No info available, so send zeroes */
pq_sendint(&buf, 0, 4);
pq_sendint(&buf, 0, 2);
}
}
/* If column is a domain, send the base type and typmod instead */
atttypid = getBaseTypeAndTypmod(atttypid, &atttypmod);
pq_sendint(&buf, (int) atttypid, sizeof(atttypid));
pq_sendint(&buf, att->attlen, sizeof(att->attlen));
pq_sendint(&buf, atttypmod, sizeof(atttypmod));
/* format info appears in protocol 3.0 and up */
if (proto >= 3)
{
if (formats)
pq_sendint(&buf, formats[i], 2);
else
pq_sendint(&buf, 0, 2);
}
pq_sendstring(buf, NameStr(att->attname));
/* column ID only info appears in protocol 3.0 and up */
pq_sendint32(buf, atttypid);
pq_sendint16(buf, att->attlen);
pq_sendint32(buf, atttypmod);
/* format info only appears in protocol 3.0 and up */
}
pq_endmessage(&buf);
}
/*