Updated db readme

Author: patrickTingen

.gitignore

@@ -2,7 +2,15 @@
 *.propath
 *.r
 .settings/
-db/
+db/xrefdb-empty.zip
+db/xrefdb.db
+db/xrefdb.lk
+db/xrefdb.d1
+db/xrefdb.b1
+db/xrefdb.lic
+db/xrefdb.lg
+db/xrefdb_7.d1
+db/xrefdb_8.d1
 html/
 palcos/
 src.debug/

db/readme.md

@@ -0,0 +1,20 @@
+# Tables in the db
+
+| Table | Description |
+| --- | ---- |
+| xref_XmlFile | XML files with xref info |
+| xref_ObjectType | Type of xref object (file, field etc) |
+| xref_RelationType | Type of relation between 2 xref objects |
+| xref_Object | Element in the XREF file (programs, fields, includes etc) |
+| xref_Relation | Relation between 2 xref objects |
+
+After compiling, the XML files are read into the xref_XmlFile table and then processed. All references in the XML file are then stored in xref_Relation. When saving this, the master tables xref_ObjectType, xref_RelationType and xref_Object are updated if needed. 
+
+When all is loaded, you should end up with 1 xref_XmlFile record for each .w, .p or .cls file, a handful of object- and relation types, a couple of thousand xref_Object records and a whole lot of xref_Relation records. Depending on your application this can easily run into hundreds of thousands. Typical application:
+| Table | Nr of records |
+| --- | ----: |
+| xref_XmlFile | 1382 |
+| xref_ObjectType | 14 |
+| xref_RelationType | 34 |
+| xref_Object | 9.423 |
+| xref_Relation | 185.322 |