Playlist copy songs¶

One song as a platform's copy of the playlist held it at the last synchronization.

This page is the dictionary for the table. It holds the definition and purpose of every field, and it is where a field is changed.

Fields¶

Field	Key	Type	Required	Allowed values or link	Definition	Purpose
`Playlist_Copy`	`PLAYLIST_COPY_SONGS.PLAYLIST_COPY`	Link to one row	Yes	Row of Playlist_Copies	A link to the copy that held the song.	Keeps the last synchronized state of each copy.
`Song`	`PLAYLIST_COPY_SONGS.SONG`	Link to one row	Yes	Row of Songs	A link to the Songs row that the copy held.	Lets a later synchronization tell a removed song from one that has not arrived.
`Position`	`PLAYLIST_COPY_SONGS.POSITION`	Whole number			The place of the song in the copy, counted from 1. Blank when the platform keeps no order.	Compares the order on platforms that keep one.
`Platform_Added_Time`	`PLAYLIST_COPY_SONGS.PLATFORM_ADDED_TIME`	Date and time (UTC)			The moment the platform says the song was added. Blank when the platform does not say.	Decides which side wins when two platforms disagree.
`Seen_Time`	`PLAYLIST_COPY_SONGS.SEEN_TIME`	Date and time (UTC)	Yes		The moment VeeJay last saw the song on the copy.	Shows how old the record of the copy is.

Constraints¶

What the database enforces on each field, beyond its type. A field that is not listed has no default, no uniqueness, no range and no reference. Every field marked Required is NOT NULL.

Field	Range or pattern	Refers to
`Playlist_Copy`		core_Playlist_Copies
`Song`		core_Songs
`Position`	1 or more
`Platform_Added_Time`	a real instant, YYYY-MM-DDTHH:MM:SSZ
`Seen_Time`	a real instant, YYYY-MM-DDTHH:MM:SSZ

Rules across fields:

A song appears once in a copy: the pair Playlist_Copy and Song is unique.

The table is core_Playlist_Copy_Songs. Every link refuses a missing target and refuses the deletion of a row that another row still points to.