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author
Neil Conway
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Attached is a patch that replaces a bunch of places where StringInfos
are unnecessarily allocated on the heap rather than the stack. If the StringInfo doesn't outlive the stack frame in which it is created, there is no need to allocate it on the heap via makeStringInfo() -- stack allocation is faster. While it's not a big deal unless the code is in a critical path, I don't see a reason not to save a few cycles -- using stack allocation is not less readable. I also cleaned up a bit of code along the way: moved variable declarations into a more tightly-enclosing scope where possible, fixed some pointless copying of strings in dblink, etc.
1 parent 8e5a10d commit 0d9742f

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5 files changed

+126
-140
lines changed

5 files changed

+126
-140
lines changed

‎contrib/dblink/dblink.c

Lines changed: 58 additions & 67 deletions
Original file line numberDiff line numberDiff line change
@@ -301,11 +301,12 @@ dblink_open(PG_FUNCTION_ARGS)
301301
char *curname = NULL;
302302
char *sql = NULL;
303303
char *conname = NULL;
304-
StringInfo str = makeStringInfo();
304+
StringInfoData buf;
305305
remoteConn *rconn = NULL;
306306
bool fail = true; /* default to backward compatible behavior */
307307

308308
DBLINK_INIT;
309+
initStringInfo(&buf);
309310

310311
if (PG_NARGS() == 2)
311312
{
@@ -361,8 +362,8 @@ dblink_open(PG_FUNCTION_ARGS)
361362
if (rconn->newXactForCursor)
362363
(rconn->openCursorCount)++;
363364

364-
appendStringInfo(str, "DECLARE %s CURSOR FOR %s", curname, sql);
365-
res = PQexec(conn, str->data);
365+
appendStringInfo(&buf, "DECLARE %s CURSOR FOR %s", curname, sql);
366+
res = PQexec(conn, buf.data);
366367
if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
367368
{
368369
if (fail)
@@ -389,12 +390,13 @@ dblink_close(PG_FUNCTION_ARGS)
389390
PGresult *res = NULL;
390391
char *curname = NULL;
391392
char *conname = NULL;
392-
StringInfo str = makeStringInfo();
393+
StringInfoData buf;
393394
char *msg;
394395
remoteConn *rconn = NULL;
395396
bool fail = true; /* default to backward compatible behavior */
396397

397398
DBLINK_INIT;
399+
initStringInfo(&buf);
398400

399401
if (PG_NARGS() == 1)
400402
{
@@ -432,10 +434,10 @@ dblink_close(PG_FUNCTION_ARGS)
432434
else
433435
conn = rconn->conn;
434436

435-
appendStringInfo(str, "CLOSE %s", curname);
437+
appendStringInfo(&buf, "CLOSE %s", curname);
436438

437439
/* close the cursor */
438-
res = PQexec(conn, str->data);
440+
res = PQexec(conn, buf.data);
439441
if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
440442
{
441443
if (fail)
@@ -493,7 +495,7 @@ dblink_fetch(PG_FUNCTION_ARGS)
493495
if (SRF_IS_FIRSTCALL())
494496
{
495497
PGconn *conn = NULL;
496-
StringInfo str = makeStringInfo();
498+
StringInfoData buf;
497499
char *curname = NULL;
498500
int howmany = 0;
499501
bool fail = true; /* default to backward compatible */
@@ -542,6 +544,9 @@ dblink_fetch(PG_FUNCTION_ARGS)
542544
if (!conn)
543545
DBLINK_CONN_NOT_AVAIL;
544546

547+
initStringInfo(&buf);
548+
appendStringInfo(&buf, "FETCH %d FROM %s", howmany, curname);
549+
545550
/* create a function context for cross-call persistence */
546551
funcctx = SRF_FIRSTCALL_INIT();
547552

@@ -550,9 +555,7 @@ dblink_fetch(PG_FUNCTION_ARGS)
550555
*/
551556
oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
552557

553-
appendStringInfo(str, "FETCH %d FROM %s", howmany, curname);
554-
555-
res = PQexec(conn, str->data);
558+
res = PQexec(conn, buf.data);
556559
if (!res ||
557560
(PQresultStatus(res) != PGRES_COMMAND_OK &&
558561
PQresultStatus(res) != PGRES_TUPLES_OK))
@@ -1547,13 +1550,14 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
15471550
HeapTuple tuple;
15481551
TupleDesc tupdesc;
15491552
int natts;
1550-
StringInfo str = makeStringInfo();
1551-
char *sql;
1553+
StringInfoData buf;
15521554
char *val;
15531555
int16 key;
15541556
int i;
15551557
bool needComma;
15561558

1559+
initStringInfo(&buf);
1560+
15571561
/* get relation name including any needed schema prefix and quoting */
15581562
relname = generate_relation_name(relid);
15591563

@@ -1570,7 +1574,7 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
15701574
(errcode(ERRCODE_CARDINALITY_VIOLATION),
15711575
errmsg("source row not found")));
15721576

1573-
appendStringInfo(str, "INSERT INTO %s(", relname);
1577+
appendStringInfo(&buf, "INSERT INTO %s(", relname);
15741578

15751579
needComma = false;
15761580
for (i = 0; i < natts; i++)
@@ -1579,14 +1583,14 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
15791583
continue;
15801584

15811585
if (needComma)
1582-
appendStringInfo(str, ",");
1586+
appendStringInfo(&buf, ",");
15831587

1584-
appendStringInfo(str, "%s",
1588+
appendStringInfoString(&buf,
15851589
quote_ident_cstr(NameStr(tupdesc->attrs[i]->attname)));
15861590
needComma = true;
15871591
}
15881592

1589-
appendStringInfo(str, ") VALUES(");
1593+
appendStringInfo(&buf, ") VALUES(");
15901594

15911595
/*
15921596
* remember attvals are 1 based
@@ -1598,7 +1602,7 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
15981602
continue;
15991603

16001604
if (needComma)
1601-
appendStringInfo(str, ",");
1605+
appendStringInfo(&buf, ",");
16021606

16031607
if (tgt_pkattvals != NULL)
16041608
key = get_attnum_pk_pos(pkattnums, pknumatts, i + 1);
@@ -1612,21 +1616,17 @@ get_sql_insert(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
16121616

16131617
if (val != NULL)
16141618
{
1615-
appendStringInfo(str, "%s", quote_literal_cstr(val));
1619+
appendStringInfoString(&buf, quote_literal_cstr(val));
16161620
pfree(val);
16171621
}
16181622
else
1619-
appendStringInfo(str, "NULL");
1623+
appendStringInfo(&buf, "NULL");
16201624
needComma = true;
16211625
}
1622-
appendStringInfo(str, ")");
1626+
appendStringInfo(&buf, ")");
16231627

1624-
sql = pstrdup(str->data);
1625-
pfree(str->data);
1626-
pfree(str);
16271628
relation_close(rel, AccessShareLock);
1628-
1629-
return (sql);
1629+
return (buf.data);
16301630
}
16311631

16321632
static char *
@@ -1636,10 +1636,11 @@ get_sql_delete(Oid relid, int2vector *pkattnums, int16 pknumatts, char **tgt_pka
16361636
char *relname;
16371637
TupleDesc tupdesc;
16381638
int natts;
1639-
StringInfo str = makeStringInfo();
1640-
char *sql;
1639+
StringInfoData buf;
16411640
int i;
16421641

1642+
initStringInfo(&buf);
1643+
16431644
/* get relation name including any needed schema prefix and quoting */
16441645
relname = generate_relation_name(relid);
16451646

@@ -1650,34 +1651,30 @@ get_sql_delete(Oid relid, int2vector *pkattnums, int16 pknumatts, char **tgt_pka
16501651
tupdesc = rel->rd_att;
16511652
natts = tupdesc->natts;
16521653

1653-
appendStringInfo(str, "DELETE FROM %s WHERE ", relname);
1654+
appendStringInfo(&buf, "DELETE FROM %s WHERE ", relname);
16541655
for (i = 0; i < pknumatts; i++)
16551656
{
16561657
int16 pkattnum = pkattnums->values[i];
16571658

16581659
if (i > 0)
1659-
appendStringInfo(str, " AND ");
1660+
appendStringInfo(&buf, " AND ");
16601661

1661-
appendStringInfo(str, "%s",
1662+
appendStringInfoString(&buf,
16621663
quote_ident_cstr(NameStr(tupdesc->attrs[pkattnum - 1]->attname)));
16631664

16641665
if (tgt_pkattvals == NULL)
16651666
/* internal error */
16661667
elog(ERROR, "target key array must not be NULL");
16671668

16681669
if (tgt_pkattvals[i] != NULL)
1669-
appendStringInfo(str, " = %s",
1670+
appendStringInfo(&buf, " = %s",
16701671
quote_literal_cstr(tgt_pkattvals[i]));
16711672
else
1672-
appendStringInfo(str, " IS NULL");
1673+
appendStringInfo(&buf, " IS NULL");
16731674
}
16741675

1675-
sql = pstrdup(str->data);
1676-
pfree(str->data);
1677-
pfree(str);
16781676
relation_close(rel, AccessShareLock);
1679-
1680-
return (sql);
1677+
return (buf.data);
16811678
}
16821679

16831680
static char *
@@ -1688,13 +1685,14 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
16881685
HeapTuple tuple;
16891686
TupleDesc tupdesc;
16901687
int natts;
1691-
StringInfo str = makeStringInfo();
1692-
char *sql;
1688+
StringInfoData buf;
16931689
char *val;
16941690
int16 key;
16951691
int i;
16961692
bool needComma;
16971693

1694+
initStringInfo(&buf);
1695+
16981696
/* get relation name including any needed schema prefix and quoting */
16991697
relname = generate_relation_name(relid);
17001698

@@ -1711,7 +1709,7 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
17111709
(errcode(ERRCODE_CARDINALITY_VIOLATION),
17121710
errmsg("source row not found")));
17131711

1714-
appendStringInfo(str, "UPDATE %s SET ", relname);
1712+
appendStringInfo(&buf, "UPDATE %s SET ", relname);
17151713

17161714
needComma = false;
17171715
for (i = 0; i < natts; i++)
@@ -1720,9 +1718,9 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
17201718
continue;
17211719

17221720
if (needComma)
1723-
appendStringInfo(str, ", ");
1721+
appendStringInfo(&buf, ", ");
17241722

1725-
appendStringInfo(str, "%s = ",
1723+
appendStringInfo(&buf, "%s = ",
17261724
quote_ident_cstr(NameStr(tupdesc->attrs[i]->attname)));
17271725

17281726
if (tgt_pkattvals != NULL)
@@ -1737,24 +1735,24 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
17371735

17381736
if (val != NULL)
17391737
{
1740-
appendStringInfo(str, "%s", quote_literal_cstr(val));
1738+
appendStringInfoString(&buf, quote_literal_cstr(val));
17411739
pfree(val);
17421740
}
17431741
else
1744-
appendStringInfo(str, "NULL");
1742+
appendStringInfoString(&buf, "NULL");
17451743
needComma = true;
17461744
}
17471745

1748-
appendStringInfo(str, " WHERE ");
1746+
appendStringInfo(&buf, " WHERE ");
17491747

17501748
for (i = 0; i < pknumatts; i++)
17511749
{
17521750
int16 pkattnum = pkattnums->values[i];
17531751

17541752
if (i > 0)
1755-
appendStringInfo(str, " AND ");
1753+
appendStringInfo(&buf, " AND ");
17561754

1757-
appendStringInfo(str, "%s",
1755+
appendStringInfo(&buf, "%s",
17581756
quote_ident_cstr(NameStr(tupdesc->attrs[pkattnum - 1]->attname)));
17591757

17601758
if (tgt_pkattvals != NULL)
@@ -1764,19 +1762,15 @@ get_sql_update(Oid relid, int2vector *pkattnums, int16 pknumatts, char **src_pka
17641762

17651763
if (val != NULL)
17661764
{
1767-
appendStringInfo(str, " = %s", quote_literal_cstr(val));
1765+
appendStringInfo(&buf, " = %s", quote_literal_cstr(val));
17681766
pfree(val);
17691767
}
17701768
else
1771-
appendStringInfo(str, " IS NULL");
1769+
appendStringInfo(&buf, " IS NULL");
17721770
}
17731771

1774-
sql = pstrdup(str->data);
1775-
pfree(str->data);
1776-
pfree(str);
17771772
relation_close(rel, AccessShareLock);
1778-
1779-
return (sql);
1773+
return (buf.data);
17801774
}
17811775

17821776
/*
@@ -1836,12 +1830,13 @@ get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 pknumatts, char **
18361830
Relation rel;
18371831
char *relname;
18381832
TupleDesc tupdesc;
1839-
StringInfo str = makeStringInfo();
1840-
char *sql = NULL;
1833+
StringInfoData buf;
18411834
int ret;
18421835
HeapTuple tuple;
18431836
int i;
18441837

1838+
initStringInfo(&buf);
1839+
18451840
/* get relation name including any needed schema prefix and quoting */
18461841
relname = generate_relation_name(relid);
18471842

@@ -1863,34 +1858,30 @@ get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 pknumatts, char **
18631858
* Build sql statement to look up tuple of interest Use src_pkattvals as
18641859
* the criteria.
18651860
*/
1866-
appendStringInfo(str, "SELECT * FROM %s WHERE ", relname);
1861+
appendStringInfo(&buf, "SELECT * FROM %s WHERE ", relname);
18671862

18681863
for (i = 0; i < pknumatts; i++)
18691864
{
18701865
int16 pkattnum = pkattnums->values[i];
18711866

18721867
if (i > 0)
1873-
appendStringInfo(str, " AND ");
1868+
appendStringInfo(&buf, " AND ");
18741869

1875-
appendStringInfo(str, "%s",
1870+
appendStringInfoString(&buf,
18761871
quote_ident_cstr(NameStr(tupdesc->attrs[pkattnum - 1]->attname)));
18771872

18781873
if (src_pkattvals[i] != NULL)
1879-
appendStringInfo(str, " = %s",
1874+
appendStringInfo(&buf, " = %s",
18801875
quote_literal_cstr(src_pkattvals[i]));
18811876
else
1882-
appendStringInfo(str, " IS NULL");
1877+
appendStringInfo(&buf, " IS NULL");
18831878
}
18841879

1885-
sql = pstrdup(str->data);
1886-
pfree(str->data);
1887-
pfree(str);
1888-
18891880
/*
18901881
* Retrieve the desired tuple
18911882
*/
1892-
ret = SPI_exec(sql, 0);
1893-
pfree(sql);
1883+
ret = SPI_exec(buf.data, 0);
1884+
pfree(buf.data);
18941885

18951886
/*
18961887
* Only allow one qualifying tuple

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