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Use one stringbuffer for all rows printed in printtup.c. 

This avoids newly allocating, and then possibly growing, the
stringbuffer for every row. For wide rows this can substantially
reduce memory allocator overhead, at the price of not immediately
reducing memory usage after outputting an especially wide row.

Author: Andres Freund
Discussion: https://postgr.es/m/20170914063418.sckdzgjfrsbekae4@alap3.anarazel.de
This commit is contained in:
Andres Freund 2017-10-11 16:26:35 -07:00
parent 1de09ad8eb
commit f2dec34e19
1 changed files with 25 additions and 21 deletions
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46
src/backend/access/common/printtup.c
View File

@ -57,6 +57,7 @@ typedef struct
typedef struct
{
DestReceiver pub; /* publicly-known function pointers */
StringInfoData buf; /* output buffer */
Portal portal; /* the Portal we are printing from */
bool sendDescrip; /* send RowDescription at startup? */
TupleDesc attrinfo; /* The attr info we are set up for */
@ -127,6 +128,9 @@ printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
DR_printtup *myState = (DR_printtup *) self;
Portal portal = myState->portal;
/* create buffer to be used for all messages */
initStringInfo(&myState->buf);
/*
* Create a temporary memory context that we can reset once per row to
* recover palloc'd memory. This avoids any problems with leaks inside
@ -302,7 +306,7 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
TupleDesc typeinfo = slot->tts_tupleDescriptor;
DR_printtup *myState = (DR_printtup *) self;
MemoryContext oldcontext;
StringInfoData buf;
StringInfo buf = &myState->buf;
int natts = typeinfo->natts;
int i;
@ -319,9 +323,9 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
/*
* Prepare a DataRow message (note buffer is in per-row context)
*/
pq_beginmessage(&buf, 'D');
pq_beginmessage_reuse(buf, 'D');
pq_sendint(&buf, natts, 2);
pq_sendint(buf, natts, 2);
/*
* send the attributes of this tuple
@ -333,7 +337,7 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
if (slot->tts_isnull[i])
{
pq_sendint(&buf, -1, 4);
pq_sendint(buf, -1, 4);
continue;
}
@ -354,7 +358,7 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
char *outputstr;
outputstr = OutputFunctionCall(&thisState->finfo, attr);
pq_sendcountedtext(&buf, outputstr, strlen(outputstr), false);
pq_sendcountedtext(buf, outputstr, strlen(outputstr), false);
}
else
{
@ -362,13 +366,13 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
bytea *outputbytes;
outputbytes = SendFunctionCall(&thisState->finfo, attr);
pq_sendint(&buf, VARSIZE(outputbytes) - VARHDRSZ, 4);
pq_sendbytes(&buf, VARDATA(outputbytes),
pq_sendint(buf, VARSIZE(outputbytes) - VARHDRSZ, 4);
pq_sendbytes(buf, VARDATA(outputbytes),
VARSIZE(outputbytes) - VARHDRSZ);
}
}
pq_endmessage(&buf);
pq_endmessage_reuse(buf);
/* Return to caller's context, and flush row's temporary memory */
MemoryContextSwitchTo(oldcontext);
@ -387,7 +391,7 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
TupleDesc typeinfo = slot->tts_tupleDescriptor;
DR_printtup *myState = (DR_printtup *) self;
MemoryContext oldcontext;
StringInfoData buf;
StringInfo buf = &myState->buf;
int natts = typeinfo->natts;
int i,
j,
@ -406,7 +410,7 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
/*
* tell the frontend to expect new tuple data (in ASCII style)
*/
pq_beginmessage(&buf, 'D');
pq_beginmessage_reuse(buf, 'D');
/*
* send a bitmap of which attributes are not null
@ -420,13 +424,13 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
k >>= 1;
if (k == 0) /* end of byte? */
{
pq_sendint(&buf, j, 1);
pq_sendint(buf, j, 1);
j = 0;
k = 1 << 7;
}
}
if (k != (1 << 7)) /* flush last partial byte */
pq_sendint(&buf, j, 1);
pq_sendint(buf, j, 1);
/*
* send the attributes of this tuple
@ -443,10 +447,10 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
Assert(thisState->format == 0);
outputstr = OutputFunctionCall(&thisState->finfo, attr);
pq_sendcountedtext(&buf, outputstr, strlen(outputstr), true);
pq_sendcountedtext(buf, outputstr, strlen(outputstr), true);
}
pq_endmessage(&buf);
pq_endmessage_reuse(buf);
/* Return to caller's context, and flush row's temporary memory */
MemoryContextSwitchTo(oldcontext);
@ -572,7 +576,7 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
TupleDesc typeinfo = slot->tts_tupleDescriptor;
DR_printtup *myState = (DR_printtup *) self;
MemoryContext oldcontext;
StringInfoData buf;
StringInfo buf = &myState->buf;
int natts = typeinfo->natts;
int i,
j,
@ -591,7 +595,7 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
/*
* tell the frontend to expect new tuple data (in binary style)
*/
pq_beginmessage(&buf, 'B');
pq_beginmessage_reuse(buf, 'B');
/*
* send a bitmap of which attributes are not null
@ -605,13 +609,13 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
k >>= 1;
if (k == 0) /* end of byte? */
{
pq_sendint(&buf, j, 1);
pq_sendint(buf, j, 1);
j = 0;
k = 1 << 7;
}
}
if (k != (1 << 7)) /* flush last partial byte */
pq_sendint(&buf, j, 1);
pq_sendint(buf, j, 1);
/*
* send the attributes of this tuple
@ -628,12 +632,12 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
Assert(thisState->format == 1);
outputbytes = SendFunctionCall(&thisState->finfo, attr);
pq_sendint(&buf, VARSIZE(outputbytes) - VARHDRSZ, 4);
pq_sendbytes(&buf, VARDATA(outputbytes),
pq_sendint(buf, VARSIZE(outputbytes) - VARHDRSZ, 4);
pq_sendbytes(buf, VARDATA(outputbytes),
VARSIZE(outputbytes) - VARHDRSZ);
}
pq_endmessage(&buf);
pq_endmessage_reuse(buf);
/* Return to caller's context, and flush row's temporary memory */
MemoryContextSwitchTo(oldcontext);