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

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