Hand code string to integer conversion for performance.

As benchmarks show, using libc's string-to-integer conversion is
pretty slow. At least part of the reason for that is that strtol[l]
have to be more generic than what largely is required inside pg.

This patch considerably speeds up int2/int4 input (int8 already was
already using hand-rolled code).

Most of the existing pg_atoi callers have been converted. But as one
requires pg_atoi's custom delimiter functionality, and as it seems
likely that there's external pg_atoi users, it seems sensible to just
keep pg_atoi around.

Author: Andres Freund
Reviewed-By: Robert Haas
Discussion: https://postgr.es/m/20171208214437.qgn6zdltyq5hmjpk@alap3.anarazel.de

Author: anarazel

contrib/spi/refint.c

@@ -306,7 +306,7 @@ check_foreign_key(PG_FUNCTION_ARGS)
 		/* internal error */
 		elog(ERROR, "check_foreign_key: too short %d (< 5) list of arguments", nargs);
 
-	nrefs = pg_atoi(args[0], sizeof(int), 0);
+	nrefs = pg_strtoint32(args[0]);
 	if (nrefs < 1)
 		/* internal error */
 		elog(ERROR, "check_foreign_key: %d (< 1) number of references specified", nrefs);

doc/src/sgml/sources.sgml

@@ -709,7 +709,7 @@ BETTER: could not open file %s (I/O failure)
     not helpful information.  If the error text doesn't make as much sense
     without the function name, reword it.
 <programlisting>
-BAD:    pg_atoi: error in "z": cannot parse "z"
+BAD:    pg_strtoint32: error in "z": cannot parse "z"
 BETTER: invalid input syntax for integer: "z"
 </programlisting>
    </para>

src/backend/libpq/pqmq.c

@@ -286,10 +286,10 @@ pq_parse_errornotice(StringInfo msg, ErrorData *edata)
 				edata->hint = pstrdup(value);
 				break;
 			case PG_DIAG_STATEMENT_POSITION:
-				edata->cursorpos = pg_atoi(value, sizeof(int), '\0');
+				edata->cursorpos = pg_strtoint32(value);
 				break;
 			case PG_DIAG_INTERNAL_POSITION:
-				edata->internalpos = pg_atoi(value, sizeof(int), '\0');
+				edata->internalpos = pg_strtoint32(value);
 				break;
 			case PG_DIAG_INTERNAL_QUERY:
 				edata->internalquery = pstrdup(value);
@@ -316,7 +316,7 @@ pq_parse_errornotice(StringInfo msg, ErrorData *edata)
 				edata->filename = pstrdup(value);
 				break;
 			case PG_DIAG_SOURCE_LINE:
-				edata->lineno = pg_atoi(value, sizeof(int), '\0');
+				edata->lineno = pg_strtoint32(value);
 				break;
 			case PG_DIAG_SOURCE_FUNCTION:
 				edata->funcname = pstrdup(value);

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -345,7 +345,7 @@ libpqrcv_identify_system(WalReceiverConn *conn, TimeLineID *primary_tli,
 						   ntuples, nfields, 3, 1)));
 	}
 	primary_sysid = pstrdup(PQgetvalue(res, 0, 0));
-	*primary_tli = pg_atoi(PQgetvalue(res, 0, 1), 4, 0);
+	*primary_tli = pg_strtoint32(PQgetvalue(res, 0, 1));
 	PQclear(res);
 
 	*server_version = PQserverVersion(conn->streamConn);
@@ -480,7 +480,7 @@ libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
 		if (PQnfields(res) < 2 || PQntuples(res) != 1)
 			ereport(ERROR,
 					(errmsg("unexpected result set after end-of-streaming")));
-		*next_tli = pg_atoi(PQgetvalue(res, 0, 0), sizeof(uint32), 0);
+		*next_tli = pg_strtoint32(PQgetvalue(res, 0, 0));
 		PQclear(res);
 
 		/* the result set should be followed by CommandComplete */

src/backend/tsearch/wparser_def.c

@@ -2460,13 +2460,13 @@ prsd_headline(PG_FUNCTION_ARGS)
 		char	   *val = defGetString(defel);
 
 		if (pg_strcasecmp(defel->defname, "MaxWords") == 0)
-			max_words = pg_atoi(val, sizeof(int32), 0);
+			max_words = pg_strtoint32(val);
 		else if (pg_strcasecmp(defel->defname, "MinWords") == 0)
-			min_words = pg_atoi(val, sizeof(int32), 0);
+			min_words = pg_strtoint32(val);
 		else if (pg_strcasecmp(defel->defname, "ShortWord") == 0)
-			shortword = pg_atoi(val, sizeof(int32), 0);
+			shortword = pg_strtoint32(val);
 		else if (pg_strcasecmp(defel->defname, "MaxFragments") == 0)
-			max_fragments = pg_atoi(val, sizeof(int32), 0);
+			max_fragments = pg_strtoint32(val);
 		else if (pg_strcasecmp(defel->defname, "StartSel") == 0)
 			prs->startsel = pstrdup(val);
 		else if (pg_strcasecmp(defel->defname, "StopSel") == 0)

src/backend/utils/adt/arrayutils.c

@@ -226,8 +226,7 @@ ArrayGetIntegerTypmods(ArrayType *arr, int *n)
 	result = (int32 *) palloc(*n * sizeof(int32));
 
 	for (i = 0; i < *n; i++)
-		result[i] = pg_atoi(DatumGetCString(elem_values[i]),
-							sizeof(int32), '\0');
+		result[i] = pg_strtoint32(DatumGetCString(elem_values[i]));
 
 	pfree(elem_values);
 

src/backend/utils/adt/int.c

@@ -60,7 +60,7 @@ int2in(PG_FUNCTION_ARGS)
 {
 	char	   *num = PG_GETARG_CSTRING(0);
 
-	PG_RETURN_INT16(pg_atoi(num, sizeof(int16), '\0'));
+	PG_RETURN_INT16(pg_strtoint16(num));
 }
 
 /*
@@ -265,7 +265,7 @@ int4in(PG_FUNCTION_ARGS)
 {
 	char	   *num = PG_GETARG_CSTRING(0);
 
-	PG_RETURN_INT32(pg_atoi(num, sizeof(int32), '\0'));
+	PG_RETURN_INT32(pg_strtoint32(num));
 }
 
 /*

src/backend/utils/adt/int8.c

@@ -101,6 +101,7 @@ scanint8(const char *str, bool errorOK, int64 *result)
 
 	if (!neg)
 	{
+		/* could fail if input is most negative number */
 		if (unlikely(tmp == PG_INT64_MIN))
 			goto out_of_range;
 		tmp = -tmp;

src/backend/utils/adt/numutils.c

@@ -18,6 +18,7 @@
 #include <limits.h>
 #include <ctype.h>
 
+#include "common/int.h"
 #include "utils/builtins.h"
 
 /*
@@ -108,6 +109,154 @@ pg_atoi(const char *s, int size, int c)
 	return (int32) l;
 }
 
+/*
+ * Convert input string to a signed 16 bit integer.
+ *
+ * Allows any number of leading or trailing whitespace characters. Will throw
+ * ereport() upon bad input format or overflow.
+ *
+ * NB: Accumulate input as a negative number, to deal with two's complement
+ * representation of the most negative number, which can't be represented as a
+ * positive number.
+ */
+int16
+pg_strtoint16(const char *s)
+{
+	const char *ptr = s;
+	int16		tmp = 0;
+	bool		neg = false;
+
+	/* skip leading spaces */
+	while (likely(*ptr) && isspace((unsigned char) *ptr))
+		ptr++;
+
+	/* handle sign */
+	if (*ptr == '-')
+	{
+		ptr++;
+		neg = true;
+	}
+	else if (*ptr == '+')
+		ptr++;
+
+	/* require at least one digit */
+	if (unlikely(!isdigit((unsigned char) *ptr)))
+		goto invalid_syntax;
+
+	/* process digits */
+	while (*ptr && isdigit((unsigned char) *ptr))
+	{
+		int8		digit = (*ptr++ - '0');
+
+		if (unlikely(pg_mul_s16_overflow(tmp, 10, &tmp)) ||
+			unlikely(pg_sub_s16_overflow(tmp, digit, &tmp)))
+			goto out_of_range;
+	}
+
+	/* allow trailing whitespace, but not other trailing chars */
+	while (*ptr != '\0' && isspace((unsigned char) *ptr))
+		ptr++;
+
+	if (unlikely(*ptr != '\0'))
+		goto invalid_syntax;
+
+	if (!neg)
+	{
+		/* could fail if input is most negative number */
+		if (unlikely(tmp == PG_INT16_MIN))
+			goto out_of_range;
+		tmp = -tmp;
+	}
+
+	return tmp;
+
+out_of_range:
+	ereport(ERROR,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+			 errmsg("value \"%s\" is out of range for type %s",
+					s, "smallint")));
+
+invalid_syntax:
+	ereport(ERROR,
+			(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+			 errmsg("invalid input syntax for type %s: \"%s\"",
+					"smallint", s)));
+}
+
+/*
+ * Convert input string to a signed 32 bit integer.
+ *
+ * Allows any number of leading or trailing whitespace characters. Will throw
+ * ereport() upon bad input format or overflow.
+ *
+ * NB: Accumulate input as a negative number, to deal with two's complement
+ * representation of the most negative number, which can't be represented as a
+ * positive number.
+ */
+int32
+pg_strtoint32(const char *s)
+{
+	const char *ptr = s;
+	int32		tmp = 0;
+	bool		neg = false;
+
+	/* skip leading spaces */
+	while (likely(*ptr) && isspace((unsigned char) *ptr))
+		ptr++;
+
+	/* handle sign */
+	if (*ptr == '-')
+	{
+		ptr++;
+		neg = true;
+	}
+	else if (*ptr == '+')
+		ptr++;
+
+	/* require at least one digit */
+	if (unlikely(!isdigit((unsigned char) *ptr)))
+		goto invalid_syntax;
+
+	/* process digits */
+	while (*ptr && isdigit((unsigned char) *ptr))
+	{
+		int8		digit = (*ptr++ - '0');
+
+		if (unlikely(pg_mul_s32_overflow(tmp, 10, &tmp)) ||
+			unlikely(pg_sub_s32_overflow(tmp, digit, &tmp)))
+			goto out_of_range;
+	}
+
+	/* allow trailing whitespace, but not other trailing chars */
+	while (*ptr != '\0' && isspace((unsigned char) *ptr))
+		ptr++;
+
+	if (unlikely(*ptr != '\0'))
+		goto invalid_syntax;
+
+	if (!neg)
+	{
+		/* could fail if input is most negative number */
+		if (unlikely(tmp == PG_INT32_MIN))
+			goto out_of_range;
+		tmp = -tmp;
+	}
+
+	return tmp;
+
+out_of_range:
+	ereport(ERROR,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+			 errmsg("value \"%s\" is out of range for type %s",
+					s, "integer")));
+
+invalid_syntax:
+	ereport(ERROR,
+			(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+			 errmsg("invalid input syntax for type %s: \"%s\"",
+					"integer", s)));
+}
+
 /*
  * pg_itoa: converts a signed 16-bit integer to its string representation
  *

src/backend/utils/adt/varlena.c

@@ -5155,8 +5155,8 @@ text_format(PG_FUNCTION_ARGS)
 
 				str = OutputFunctionCall(&typoutputinfo_width, value);
 
-				/* pg_atoi will complain about bad data or overflow */
-				width = pg_atoi(str, sizeof(int), '\0');
+				/* pg_strtoint32 will complain about bad data or overflow */
+				width = pg_strtoint32(str);
 
 				pfree(str);
 			}