Add resetStringInfo(), which clears the content of a StringInfo, and

fixup various places in the tree that were clearing a StringInfo by hand.
Making this function a part of the API simplifies client code slightly,
and avoids needlessly peeking inside the StringInfo interface.

contrib/tablefunc/tablefunc.c

@@ -1378,15 +1378,12 @@ build_tuplestore_recursively(char *key_fld,
 								   "incompatible.")));
 		}
 
-		for (i = 0; i < proc; i++)
-		{
-			/* start a new branch */
 		initStringInfo(&branchstr);
-
-			/* need these to check for recursion */
 		initStringInfo(&chk_branchstr);
 		initStringInfo(&chk_current_key);
 
+		for (i = 0; i < proc; i++)
+		{
 			/* initialize branch for this pass */
 			appendStringInfo(&branchstr, "%s", branch);
 			appendStringInfo(&chk_branchstr, "%s%s%s", branch_delim, branch, branch_delim);
@@ -1459,11 +1456,15 @@ build_tuplestore_recursively(char *key_fld,
 													tupstore);
 
 			/* reset branch for next pass */
+			resetStringInfo(&branchstr);
+			resetStringInfo(&chk_branchstr);
+			resetStringInfo(&chk_current_key);
+		}
+
 		xpfree(branchstr.data);
 		xpfree(chk_branchstr.data);
 		xpfree(chk_current_key.data);
 	}
-	}
 
 	return tupstore;
 }

src/backend/catalog/pg_shdepend.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/pg_shdepend.c,v 1.16 2007/01/05 22:19:25 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/pg_shdepend.c,v 1.17 2007/03/03 19:32:54 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -588,8 +588,7 @@ checkSharedDependencies(Oid classId, Oid objectId)
 		 * Note: we don't ever suppress per-database totals, which should be
 		 * OK as long as there aren't too many databases ...
 		 */
-		descs.len = 0;			/* reset to empty */
-		descs.data[0] = '\0';
+		resetStringInfo(&descs);
 
 		if (numLocalDeps > 0)
 		{

src/backend/commands/copy.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.276 2007/02/20 17:32:13 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/copy.c,v 1.277 2007/03/03 19:32:54 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -466,9 +466,7 @@ CopySendEndOfRow(CopyState cstate)
 			break;
 	}
 
-	/* Reset fe_msgbuf to empty */
-	fe_msgbuf->len = 0;
-	fe_msgbuf->data[0] = '\0';
+	resetStringInfo(fe_msgbuf);
 }
 
 /*
@@ -2193,9 +2191,7 @@ CopyReadLine(CopyState cstate)
 {
 	bool		result;
 
-	/* Reset line_buf to empty */
-	cstate->line_buf.len = 0;
-	cstate->line_buf.data[0] = '\0';
+	resetStringInfo(&cstate->line_buf);
 
 	/* Mark that encoding conversion hasn't occurred yet */
 	cstate->line_buf_converted = false;
@@ -2262,8 +2258,7 @@ CopyReadLine(CopyState cstate)
 		if (cvt != cstate->line_buf.data)
 		{
 			/* transfer converted data back to line_buf */
-			cstate->line_buf.len = 0;
-			cstate->line_buf.data[0] = '\0';
+			resetStringInfo(&cstate->line_buf);
 			appendBinaryStringInfo(&cstate->line_buf, cvt, strlen(cvt));
 			pfree(cvt);
 		}
@@ -2686,9 +2681,7 @@ CopyReadAttributesText(CopyState cstate, int maxfields, char **fieldvals)
 		return 0;
 	}
 
-	/* reset attribute_buf to empty */
-	cstate->attribute_buf.len = 0;
-	cstate->attribute_buf.data[0] = '\0';
+	resetStringInfo(&cstate->attribute_buf);
 
 	/*
 	 * The de-escaped attributes will certainly not be longer than the input
@@ -2886,9 +2879,7 @@ CopyReadAttributesCSV(CopyState cstate, int maxfields, char **fieldvals)
 		return 0;
 	}
 
-	/* reset attribute_buf to empty */
-	cstate->attribute_buf.len = 0;
-	cstate->attribute_buf.data[0] = '\0';
+	resetStringInfo(&cstate->attribute_buf);
 
 	/*
 	 * The de-escaped attributes will certainly not be longer than the input
@@ -3040,12 +3031,9 @@ CopyReadBinaryAttribute(CopyState cstate,
 				 errmsg("invalid field size")));
 
 	/* reset attribute_buf to empty, and load raw data in it */
-	cstate->attribute_buf.len = 0;
-	cstate->attribute_buf.data[0] = '\0';
-	cstate->attribute_buf.cursor = 0;
+	resetStringInfo(&cstate->attribute_buf);
 
 	enlargeStringInfo(&cstate->attribute_buf, fld_size);
-
 	if (CopyGetData(cstate, cstate->attribute_buf.data,
 					fld_size, fld_size) != fld_size)
 		ereport(ERROR,

src/backend/lib/stringinfo.c

@@ -9,7 +9,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	  $PostgreSQL: pgsql/src/backend/lib/stringinfo.c,v 1.44 2007/01/05 22:19:29 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/lib/stringinfo.c,v 1.45 2007/03/03 19:32:54 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -49,8 +49,20 @@ initStringInfo(StringInfo str)
 
 	str->data = (char *) palloc(size);
 	str->maxlen = size;
-	str->len = 0;
+	resetStringInfo(str);
+}
+
+/*
+ * resetStringInfo
+ *
+ * Reset the StringInfo: the data buffer remains valid, but its
+ * previous content, if any, is cleared.
+ */
+void
+resetStringInfo(StringInfo str)
+{
 	str->data[0] = '\0';
+	str->len = 0;
 	str->cursor = 0;
 }
 

src/backend/libpq/pqcomm.c

@@ -30,7 +30,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$PostgreSQL: pgsql/src/backend/libpq/pqcomm.c,v 1.190 2007/02/13 19:18:53 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/libpq/pqcomm.c,v 1.191 2007/03/03 19:32:54 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -860,10 +860,7 @@ pq_getstring(StringInfo s)
 {
 	int			i;
 
-	/* Reset string to empty */
-	s->len = 0;
-	s->data[0] = '\0';
-	s->cursor = 0;
+	resetStringInfo(s);
 
 	/* Read until we get the terminating '\0' */
 	for (;;)
@@ -915,10 +912,7 @@ pq_getmessage(StringInfo s, int maxlen)
 {
 	int32		len;
 
-	/* Reset message buffer to empty */
-	s->len = 0;
-	s->data[0] = '\0';
-	s->cursor = 0;
+	resetStringInfo(s);
 
 	/* Read message length word */
 	if (pq_getbytes((char *) &len, 4) == EOF)

src/backend/storage/lmgr/deadlock.c

@@ -12,7 +12,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.45 2007/03/03 18:46:40 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.46 2007/03/03 19:32:54 neilc Exp $
  *
  *	Interface:
  *
@@ -933,8 +933,7 @@ DeadLockReport(void)
 			appendStringInfoChar(&buf, '\n');
 
 		/* reset buf2 to hold next object description */
-		buf2.len = 0;
-		buf2.data[0] = '\0';
+		resetStringInfo(&buf2);
 
 		DescribeLockTag(&buf2, &info->locktag);
 

src/backend/tcop/fastpath.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/fastpath.c,v 1.95 2007/01/05 22:19:39 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/fastpath.c,v 1.96 2007/03/03 19:32:54 neilc Exp $
  *
  * NOTES
  *	  This cruft is the server side of PQfn.
@@ -480,10 +480,7 @@ parse_fcall_arguments(StringInfo msgBuf, struct fp_info * fip,
 						 argsize)));
 
 			/* Reset abuf to empty, and insert raw data into it */
-			abuf.len = 0;
-			abuf.data[0] = '\0';
-			abuf.cursor = 0;
-
+			resetStringInfo(&abuf);
 			appendBinaryStringInfo(&abuf,
 								   pq_getmsgbytes(msgBuf, argsize),
 								   argsize);
@@ -613,10 +610,7 @@ parse_fcall_arguments_20(StringInfo msgBuf, struct fp_info * fip,
 						 argsize)));
 
 		/* Reset abuf to empty, and insert raw data into it */
-		abuf.len = 0;
-		abuf.data[0] = '\0';
-		abuf.cursor = 0;
-
+		resetStringInfo(&abuf);
 		appendBinaryStringInfo(&abuf,
 							   pq_getmsgbytes(msgBuf, argsize),
 							   argsize);

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.526 2007/03/02 23:37:22 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/postgres.c,v 1.527 2007/03/03 19:32:54 neilc Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -205,10 +205,7 @@ InteractiveBackend(StringInfo inBuf)
 	printf("backend> ");
 	fflush(stdout);
 
-	/* Reset inBuf to empty */
-	inBuf->len = 0;
-	inBuf->data[0] = '\0';
-	inBuf->cursor = 0;
+	resetStringInfo(inBuf);
 
 	for (;;)
 	{

src/backend/utils/adt/rowtypes.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/rowtypes.c,v 1.18 2007/01/05 22:19:42 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/rowtypes.c,v 1.19 2007/03/03 19:32:55 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -168,8 +168,7 @@ record_in(PG_FUNCTION_ARGS)
 			/* Extract string for this column */
 			bool		inquote = false;
 
-			buf.len = 0;
-			buf.data[0] = '\0';
+			resetStringInfo(&buf);
 			while (inquote || !(*ptr == ',' || *ptr == ')'))
 			{
 				char		ch = *ptr++;

src/backend/utils/adt/xml.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.33 2007/03/01 14:52:04 petere Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.34 2007/03/03 19:32:55 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -835,8 +835,7 @@ xml_init(void)
 	else
 	{
 		/* Reset pre-existing buffer to empty */
-		xml_err_buf->data[0] = '\0';
-		xml_err_buf->len = 0;
+		resetStringInfo(xml_err_buf);
 	}
 	/* Now that xml_err_buf exists, safe to call xml_errorHandler */
 	xmlSetGenericErrorFunc(NULL, xml_errorHandler);
@@ -1197,8 +1196,7 @@ xml_ereport(int level, int sqlcode,
 	if (xml_err_buf->len > 0)
 	{
 		detail = pstrdup(xml_err_buf->data);
-		xml_err_buf->data[0] = '\0';
-		xml_err_buf->len = 0;
+		resetStringInfo(xml_err_buf);
 	}
 	else
 		detail = NULL;

src/include/lib/stringinfo.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/lib/stringinfo.h,v 1.33 2007/01/05 22:19:55 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/lib/stringinfo.h,v 1.34 2007/03/03 19:32:55 neilc Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -78,6 +78,13 @@ extern StringInfo makeStringInfo(void);
  */
 extern void initStringInfo(StringInfo str);
 
+/*------------------------
+ * resetStringInfo
+ * Clears the current content of the StringInfo, if any. The
+ * StringInfo remains valid.
+ */
+extern void resetStringInfo(StringInfo str);
+
 /*------------------------
  * appendStringInfo
  * Format text data under the control of fmt (an sprintf-style format string)