Update README.md

README.md

@@ -16,8 +16,49 @@ The Peewee ORM config file is provided too, plz check it for more information. (
 The original data is from the official dump of the posts info.<br>
 Check this [link](https://console.cloud.google.com/storage/browser/danbooru_public/data) for more info.
 
-**The ID range of this dataset(\~7111459) is slightly larger then the danbooru2023 dataset(\~6899125)**
+**The ID range of this dataset(\~7111459) is slightly larger then the danbooru2023 dataset(\~6899125)** <br>
+**This dataset have 7073868 entries**
 
+## Details
+This section contains some details that you need to be aware of if you want to use other ORM system or use plain SQL query to utilize this database.
+
+#### Custom Enum Fields
+Some fields in Post/Tags use my custom enum field to store type/category or something like that:
+
+* Post.rating
+  * 0: general
+  * 1: sensitive
+  * 2: questionable
+  * 3: explicit
+* Tag.type
+  * 0: general
+  * 1: artist
+  * 2: character
+  * 3: copyright
+  * 4: meta
+
+#### Tag List
+SQLite doesn't support any arrayfield or many-to-many relationship natively.<br>
+So I use a custom TextField to store ids of tags belongs to a Post.
+
+The basic idea is to use 2 unique symbol for start/end of the number. And use 36-base number<br>
+(python support converting n-base number into integer natively, numpy have utils to convert integer into n-base number)
+
+I use $xxx# format, so when you want to utilize the FTS table to search tag_list, use $<36-base number# to find if the tag is in the tag-list.
+
+
+#### Utils
+if you think above details are too complicated, just use the db_utils.py and other PeeWee API to utilize this database.
+I also provide a write_csv.py for exporting whole dataset into csv for data analysis.
+
+
+## License
+The source code, database file of this repo is licensed under MiT License.<br>
+**Notice**: The license doesn't cover the "content" of the database.<br>
+All the content is from official danbooru dumps for posts' meta.
+
+
+## Acknowledgement
 Thx for AngelBottomless for fixing wrong entries and add more entries into this dataset:<br>
 https://huggingface.co/datasets/AngelBottomless/danbooru-2023-sqlite-fixed-7110548