Speed up byteain by not parsing traditional-style input twice.

Instead of laboriously computing the exact output length, use strlen to get an upper bound cheaply. (This is still O(N) of course, but the constant factor is a lot less.) This will typically result in overallocating the output datum, but that's of little concern since it's a short-lived allocation in just about all use-cases. A simple microbenchmark showed about 40% speedup for long input strings. While here, make some cosmetic cleanups and add a test case that covers the double-backslash code path in byteain and byteaout. Author: Steven Niu <niushiji@gmail.com> Reviewed-by: Kirill Reshke <reshkekirill@gmail.com> Reviewed-by: Stepan Neretin <slpmcf@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/ca315729-140b-426e-81a6-6cd5cfe7ecc5@gmail.com

Author: tglsfdc

src/backend/utils/adt/bytea.c

@@ -182,27 +182,21 @@ bytea_overlay(bytea *t1, bytea *t2, int sp, int sl)
  *
  *	Non-printable characters must be passed as '\nnn' (octal) and are
  *	converted to internal form. '\' must be passed as '\\'.
- *	ereport(ERROR, ...) if bad form.
- *
- *	BUGS:
- *	The input is scanned twice.
- *	The error checking of input is minimal.
  */
 Datum
 byteain(PG_FUNCTION_ARGS)
 {
 char *inputText = PG_GETARG_CSTRING(0);
 Node *escontext = fcinfo->context;
+size_tlen = strlen(inputText);
+size_tbc;
 char *tp;
 char *rp;
-intbc;
 bytea *result;
 
 /* Recognize hex input */
 if (inputText[0] == '\\' && inputText[1] == 'x')
 {
-size_tlen = strlen(inputText);
-
 bc = (len - 2) / 2 + VARHDRSZ;/* maximum possible length */
 result = palloc(bc);
 bc = hex_decode_safe(inputText + 2, len - 2, VARDATA(result),
@@ -213,70 +207,47 @@ byteain(PG_FUNCTION_ARGS)
 }
 
 /* Else, it's the traditional escaped style */
-for (bc = 0, tp = inputText; *tp != '\0'; bc++)
-{
-if (tp[0] != '\\')
-tp++;
-else if ((tp[0] == '\\') &&
- (tp[1] >= '0' && tp[1] <= '3') &&
- (tp[2] >= '0' && tp[2] <= '7') &&
- (tp[3] >= '0' && tp[3] <= '7'))
-tp += 4;
-else if ((tp[0] == '\\') &&
- (tp[1] == '\\'))
-tp += 2;
-else
-{
-/*
- * one backslash, not followed by another or ### valid octal
- */
-ereturn(escontext, (Datum) 0,
-(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
- errmsg("invalid input syntax for type %s", "bytea")));
-}
-}
-
-bc += VARHDRSZ;
-
-result = (bytea *) palloc(bc);
-SET_VARSIZE(result, bc);
+result = (bytea *) palloc(len + VARHDRSZ);/* maximum possible length */
 
 tp = inputText;
 rp = VARDATA(result);
 while (*tp != '\0')
 {
 if (tp[0] != '\\')
 *rp++ = *tp++;
-else if ((tp[0] == '\\') &&
- (tp[1] >= '0' && tp[1] <= '3') &&
+else if ((tp[1] >= '0' && tp[1] <= '3') &&
  (tp[2] >= '0' && tp[2] <= '7') &&
  (tp[3] >= '0' && tp[3] <= '7'))
 {
-bc = VAL(tp[1]);
-bc <<= 3;
-bc += VAL(tp[2]);
-bc <<= 3;
-*rp++ = bc + VAL(tp[3]);
+intv;
+
+v = VAL(tp[1]);
+v <<= 3;
+v += VAL(tp[2]);
+v <<= 3;
+*rp++ = v + VAL(tp[3]);
 
 tp += 4;
 }
-else if ((tp[0] == '\\') &&
- (tp[1] == '\\'))
+else if (tp[1] == '\\')
 {
 *rp++ = '\\';
 tp += 2;
 }
 else
 {
 /*
- * We should never get here. The first pass should not allow it.
+ * one backslash, not followed by another or ### valid octal
  */
 ereturn(escontext, (Datum) 0,
 (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
  errmsg("invalid input syntax for type %s", "bytea")));
 }
 }
 
+bc = rp - VARDATA(result);/* actual length */
+SET_VARSIZE(result, bc + VARHDRSZ);
+
 PG_RETURN_BYTEA_P(result);
 }
 

src/test/regress/expected/strings.out

@@ -236,6 +236,12 @@ SELECT E'De\\678dBeEf'::bytea;
 ERROR: invalid input syntax for type bytea
 LINE 1: SELECT E'De\\678dBeEf'::bytea;
  ^
+SELECT E'DeAd\\\\BeEf'::bytea;
+ bytea 
+----------------------
+ \x446541645c42654566
+(1 row)
+
 SELECT reverse(''::bytea);
  reverse 
 ---------
@@ -291,6 +297,12 @@ SELECT E'De\\123dBeEf'::bytea;
  DeSdBeEf
 (1 row)
 
+SELECT E'DeAd\\\\BeEf'::bytea;
+ bytea 
+------------
+ DeAd\\BeEf
+(1 row)
+
 -- Test non-error-throwing API too
 SELECT pg_input_is_valid(E'\\xDeAdBeE', 'bytea');
  pg_input_is_valid 

src/test/regress/sql/strings.sql

@@ -76,6 +76,7 @@ SELECT E'De\\000dBeEf'::bytea;
 SELECT E'De\123dBeEf'::bytea;
 SELECT E'De\\123dBeEf'::bytea;
 SELECT E'De\\678dBeEf'::bytea;
+SELECT E'DeAd\\\\BeEf'::bytea;
 
 SELECT reverse(''::bytea);
 SELECT reverse('\xaa'::bytea);
@@ -88,6 +89,7 @@ SELECT E'\\xDe00BeEf'::bytea;
 SELECT E'DeAdBeEf'::bytea;
 SELECT E'De\\000dBeEf'::bytea;
 SELECT E'De\\123dBeEf'::bytea;
+SELECT E'DeAd\\\\BeEf'::bytea;
 
 -- Test non-error-throwing API too
 SELECT pg_input_is_valid(E'\\xDeAdBeE', 'bytea');