Remove restriction on SQL block length in isolationtester scanner.

specscanner.l had a fixed limit of 1024 bytes on the length of
individual SQL stanzas in an isolation test script.  People are
starting to run into that, so fix it by making the buffer resizable.

Once we allow this in HEAD, it seems inevitable that somebody will
try to back-patch a test that exceeds the old limit, so back-patch
this change as a preventive measure.

Daniel Gustafsson

Discussion: https://postgr.es/m/8D628BE4-6606-4FF6-A3FF-8B2B0E9B43D0@yesql.se

src/test/isolation/specscanner.l

@@ -12,8 +12,10 @@
 
 static int	yyline = 1;			/* line number for error reporting */
 
-static char litbuf[1024];
-static int litbufpos = 0;
+#define LITBUF_INIT	1024		/* initial size of litbuf */
+static char *litbuf = NULL;
+static size_t litbufsize = 0;
+static size_t litbufpos = 0;
 
 static void addlitchar(char c);
 
@@ -41,6 +43,11 @@ comment			("#"{non_newline}*)
 
 %%
 
+%{
+	litbuf = pg_malloc(LITBUF_INIT);
+	litbufsize = LITBUF_INIT;
+%}
+
 permutation		{ return PERMUTATION; }
 session			{ return SESSION; }
 setup			{ return SETUP; }
@@ -100,10 +107,12 @@ teardown		{ return TEARDOWN; }
 static void
 addlitchar(char c)
 {
-	if (litbufpos >= sizeof(litbuf) - 1)
+	/* We must always leave room to add a trailing \0 */
+	if (litbufpos >= litbufsize - 1)
 	{
-		fprintf(stderr, "SQL step too long\n");
-		exit(1);
+		/* Double the size of litbuf if it gets full */
+		litbufsize += litbufsize;
+		litbuf = pg_realloc(litbuf, litbufsize);
 	}
 	litbuf[litbufpos++] = c;
 }