Dynamodb Conecpts
(this post if part of the material I cover in my devops course)
Core DynamoDB Objects
- Tables
DynamoDB stores data in tables. A table is a collection of data.
- Items
Each table contains zero or more items. An item is a group of attributes that is uniquely identifiable among all of the other items.
- Attributes
Each item is composed of one or more attributes. An attribute is a fundamental data element, something that does not need to be broken down any further.
Example: People Table
- Here's an example for a dynamodb table:
1{
2 "PersonID": 101,
3 "LastName": "Smith",
4 "FirstName": "Fred",
5 "Phone": "555-4321"
6}
7
8{
9 "PersonID": 102,
10 "LastName": "Jones",
11 "FirstName": "Mary",
12 "Address": {
13 "Street": "123 Main",
14 "City": "Anytown",
15 "State": "OH",
16 "ZIPCode": 12345
17 }
18}
19
20{
21 "PersonID": 103,
22 "LastName": "Stephens",
23 "FirstName": "Howard",
24 "Address": {
25 "Street": "123 Main",
26 "City": "London",
27 "PostalCode": "ER3 5K8"
28 },
29 "FavoriteColor": "Blue"
30}
- This is a single table with three items.
- Note that the items do not have a fixed structure, so the table is schemaless.
- Most of the attributes are scalar, which means that they can have only one value. Strings and numbers are common examples of scalars.
- Some of the items have a nested attribute (like Address). DynamoDB supports nested attributes up to 32 levels deep.
Keys
- Each item in the table has a unique identifier, or primary key, that distinguishes the item from all of the others in the table.
- In the People table (previous example), the primary key consists of one attribute (PersonID).
- Sometimes, the primary key can be made of two keys.
Here's an example:
1{
2 "Artist": "No One You Know",
3 "SongTitle": "My Dog Spot",
4 "AlbumTitle": "Hey Now",
5 "Price": 1.98,
6 "Genre": "Country",
7 "CriticRating": 8.4
8}
9
10{
11 "Artist": "No One You Know",
12 "SongTitle": "Somewhere Down The Road",
13 "AlbumTitle": "Somewhat Famous",
14 "Genre": "Country",
15 "CriticRating": 8.4,
16 "Year": 1984
17}
18
19{
20 "Artist": "The Acme Band",
21 "SongTitle": "Still in Love",
22 "AlbumTitle": "The Buck Starts Here",
23 "Price": 2.47,
24 "Genre": "Rock",
25 "PromotionInfo": {
26 "RadioStationsPlaying": [
27 "KHCR",
28 "KQBX",
29 "WTNR",
30 "WJJH"
31 ],
32 "TourDates": {
33 "Seattle": "20150622",
34 "Cleveland": "20150630"
35 },
36 "Rotation": "Heavy"
37 }
38}
39
40{
41 "Artist": "The Acme Band",
42 "SongTitle": "Look Out, World",
43 "AlbumTitle": "The Buck Starts Here",
44 "Price": 0.99,
45 "Genre": "Rock"
46}
- The primary key for Music consists of two attributes (Artist and SongTitle).
- Each item in the table must have these two attributes. The combination of Artist and SongTitle distinguishes each item in the table from all of the others.
- When a table has a primary key made of one attribute, this attribute is the partition key.
- When a table has a primary key made of two keys, one is the partition key, and the other is the sort key
- In our example Artist was the partition key.