> The previous patch fixed an infinite recursion bug in

> contrib/tablefunc/tablefunc.c:connectby. But, other unmanageable error
> seems to occur even if a table has commonplace tree data(see below).
>
> I would think the patch, ancestor check, should be
>
>   if (strstr(branch_delim || branchstr->data || branch_delim,
>                        branch_delim || current_key || branch_delim))
>
> This is my image, not a real code. However, if branchstr->data includes
> branch_delim, my image will not be perfect.

Good point. Thank you Masaru for the suggested fix.

Attached is a patch to fix the bug found by Masaru. His example now
produces:

regression=# SELECT * FROM connectby('connectby_tree', 'keyid',
'parent_keyid', '11', 0, '-') AS t(keyid int, parent_keyid int, level
int,
branch text);
  keyid | parent_keyid | level |  branch

-------+--------------+-------+----------
     11 |              |     0 | 11
     10 |           11 |     1 | 11-10
    111 |           11 |     1 | 11-111
      1 |          111 |     2 | 11-111-1
(4 rows)

While making the patch I also realized that the "no show branch" form of
the  function was not going to work very well for recursion detection.
Therefore  there is now a default branch delimiter ('~') that is used
internally, for  that case, to enable recursion detection to work. If
you need a different  delimiter for your specific data, you will have to
use the "show branch" form  of the function.

Joe Conway

contrib/tablefunc/README.tablefunc

@@ -365,7 +365,9 @@ Inputs
 
   branch_delim
 
-    if optional branch value is desired, this string is used as the delimiter
+    If optional branch value is desired, this string is used as the delimiter.
+    When not provided, a default value of '~' is used for internal 
+    recursion detection only, and no "branch" field is returned.
 
 Outputs
 
@@ -388,7 +390,10 @@ Notes
      the level value output
 
   3. If the branch field is not desired, omit both the branch_delim input
-     parameter *and* the branch field in the query column definition
+     parameter *and* the branch field in the query column definition. Note
+     that when branch_delim is not provided, a default value of '~' is used
+     for branch_delim for internal recursion detection, even though the branch
+     field is not returned.
 
   4. If the branch field is desired, it must be the forth column in the query
      column definition, and it must be type TEXT

contrib/tablefunc/tablefunc.c

@@ -652,6 +652,9 @@ connectby_text(PG_FUNCTION_ARGS)
 		branch_delim = GET_STR(PG_GETARG_TEXT_P(5));
 		show_branch = true;
 	}
+	else
+		/* default is no show, tilde for the delimiter */
+		branch_delim = pstrdup("~");
 
 	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
 	oldcontext = MemoryContextSwitchTo(per_query_ctx);
@@ -798,10 +801,16 @@ build_tuplestore_recursively(char *key_fld,
 		char	   *current_branch;
 		char	  **values;
 		StringInfo	branchstr = NULL;
+		StringInfo	chk_branchstr = NULL;
+		StringInfo	chk_current_key = NULL;
 
 		/* start a new branch */
 		branchstr = makeStringInfo();
 
+		/* need these to check for recursion */
+		chk_branchstr = makeStringInfo();
+		chk_current_key = makeStringInfo();
+
 		if (show_branch)
 			values = (char **) palloc(CONNECTBY_NCOLS * sizeof(char *));
 		else
@@ -854,22 +863,24 @@ build_tuplestore_recursively(char *key_fld,
 		{
 			/* initialize branch for this pass */
 			appendStringInfo(branchstr, "%s", branch);
+			appendStringInfo(chk_branchstr, "%s%s%s", branch_delim, branch, branch_delim);
 
 			/* get the next sql result tuple */
 			spi_tuple = tuptable->vals[i];
 
 			/* get the current key and parent */
 			current_key = SPI_getvalue(spi_tuple, spi_tupdesc, 1);
+			appendStringInfo(chk_current_key, "%s%s%s", branch_delim, current_key, branch_delim);
 			current_key_parent = pstrdup(SPI_getvalue(spi_tuple, spi_tupdesc, 2));
 
-			/* check to see if this key is also an ancestor */
-			if (strstr(branchstr->data, current_key))
-				elog(ERROR, "infinite recursion detected");
-
 			/* get the current level */
 			sprintf(current_level, "%d", level);
 
-			/* extend the branch */
+			/* check to see if this key is also an ancestor */
+			if (strstr(chk_branchstr->data, chk_current_key->data))
+				elog(ERROR, "infinite recursion detected");
+
+			/* OK, extend the branch */
 			appendStringInfo(branchstr, "%s%s", branch_delim, current_key);
 			current_branch = branchstr->data;
 
@@ -913,6 +924,12 @@ build_tuplestore_recursively(char *key_fld,
 			/* reset branch for next pass */
 			xpfree(branchstr->data);
 			initStringInfo(branchstr);
+
+			xpfree(chk_branchstr->data);
+			initStringInfo(chk_branchstr);
+
+			xpfree(chk_current_key->data);
+			initStringInfo(chk_current_key);
 		}
 	}