支持内容外键，即某一列指向redis中的一个key，将其变成文件路径。

test/table_info.conf

@@ -7,10 +7,10 @@
 #do_merege [yes/no]
 #cross cache [number]
 #quick mode [quickon/quickoff], default [quickoff]
-#For ip/intval/digest/compile/group
+#For ip/intval/digest/compile/group table.
 #id	name	type
 #
-#For plugin table
+#For plugin table. The first column's id is 1. 0 as not speicified.
 #id	name	type	valid_column tag_column
 #
 #For expr/expr_plus Table
@@ -27,4 +27,5 @@
 8	HTTP_REGION	expr_plus	GBK	GBK	no	0
 9	SIM_URL	similar	--
 10	IMAGE_FP	expr	UTF8	UTF8	yes	128	quickoff
-11	TEST_EFFECTIVE_RANGE_TABLE	plugin	4	5	--
+11	TEST_EFFECTIVE_RANGE_TABLE	plugin	valid_pos=4;tag_pos=5;	--
+12	TEST_EXETERN_LINK	plugin valid_pos=3;foreign_pos=6,7;