This is an initial review of the Akonadi/MySQL Entity-Relationship Diagram (ERD).
**Model Notation**
[[ https://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model#Crow's_foot_notation | Crow's Foot ]]
**Crow's Foot Refresher**
The symbols at the end of each relationship define the minimum and maximum cardinality:
- | - one
- o = zero
- < = many
For example given the following:
```
[parent] -------o< [child]
```
- Each **[parent]** may have //zero to many// **[child]**'s
- Each **[child]** may have //one and only// one **[parent]**
**Observations**
- There are many standalone entities (e.g. **[collectionpimitemrelation]**, **[tagtypetable]**, **[parttable]**, etc). I would think that //somehow// they would be related to some other entity.
- Perhaps this is my own ignorance of Akonadi but at first blush, I see several //islands// of relationships. For example, here are couple:
# **[resourcetable]/[tagremoteidresourcerelationtable]**
# **[collectiontable]/[pimitemtable]/[relationtable]/[pimitemtagrelation]/[mimetypetable]**
- The relationship **[mimetypetable]/[pimitemtable]** is defined such that we can have a **[pimitemtable]** row with no **[mimetypetable]** defined. I suspect that this is per specification but I want to be sure. :)
- //Minor// - personally, I don't like to embed the type of object in the name of the object. For example, //collection**table**//. This is admittedly a nitpick. ;)
- //Minor// - personally, it would be great to use underscores to separate names. I find it far easier to read **[tag_remote_id_resource_relationship_table]** than **[tagremoteidresourcerelationshiptable]** This is yet-another-nitpick.
{F5685689}
= Actionables =
Outcomes of the current discussion in no particular order of importance or severity. Can be crossed-out once implemented/fixed.
[] Eventually change Associative Tables that have Unique Key to Primary Key (like the rest) (T7846#126304)
[] Drop unnecessary indexes from **[CollectionTable]** (T7846#126304)
[] Bool-like columns should be **NOT NULL** (T7846#126596)
[] Move **[CollectionAttributeTable].type** to it's own table to de-duplicate the strings, same for **[TagAttributeTable]** (T7846#126596, T7846#126615)
[] **[PimItemTable].mimeTypeId**, **[PimItemTable].collectionId** and **[RelationTable].typeId** FKs should be **NOT NULL**