CS6320:  SW Engineering of Web Based Systems
Instructor Outline Syllabus Projects Links  

 

GAE Datastore --property values (data types you can store)

Data Type

Java type

Python type

Unicode text string (up to
500 bytes, indexed)

"Short String"

java.lang.String

unicode or str (converted to uni
code as ASCII)

Long Unicode text string
(not indexed)

"Long String"

datastore.Text

db.Text

Short byte string (up to
500 bytes, indexed)

datastore.ShortBlob

db.ByteString

Long byte string (not indexed)

datastore.Blob

db.Blob

Boolean

boolean or java.lang.Boolean

bool

Integer (64-bit)

byte, short, int, or long (converted to long)

int or long (converted to 64-bit long)

Float (double precision)

float or double (converted to double)

float

Date-time

java.util.Date

datetime.datetime

Null value

null

None

Entity key

datastore.Key

db.Key

A Google account

...api.users.User

users.User

A category (GD)

datastore.Category

db.Category

A URL (GD)

datastore.Link

db.Link

An email address (GD)

datastore.Email

db.Email

A geographical point
(GD)

datastore.GeoPt

db.GeoPt

An instant messaging
handle (GD)

datastore.IMHandle

db.IM

A phone number (GD)

datastore.PhoneNumber

db.PhoneNumber

A postal address (GD)

datastore.PostalAddress

db.PostalAddress

A user rating (GD)

datastore.Rating

db.Rating

A Blobstore key

blobstore.BlobKey

ext.blobstore.BlobKey

Package Names in JAVA only for selected data types above

more

NOTE: GD = Google Data protocol -- distinctive GAE native data types in datastore

NOTE: GeoPt is a pair of floating-point values for latitude (–90 to +90) and longitude (–180 to +180),

NOTE: Rating is an integer between 1 and 100.


NOTE: Blobstore keys refer to values in the Blobstore. (covered in Chpater 10 of your book --do as desired on your own --not covered in class)

Strings -- 2 kinds

 

Short Strings

    • indexed ( can be subject of queries ---- searching every Person entity for last_name property)
    • < 500 bytes (see api for latest value)

Long Strings

  • NOT indexed ( can NOT be subject of queries !!!!)
  • can be > 500 bytes (se

Uses UTF-8 encoding

  • some characters using multiple bytes.
  • means that the 500-byte limit for short strings is not necessarily the same as 500 Unicode characters.

.

Blobs and Blobstore (THIS IS DIFFERENT SERVICE THAN DATASTORE!!!!)

  • Data of No format

  • Bytes are preserved

  • Good for images, movies, media

  • Indexed (Short Blob) or Non Indexed (Blob) variety

  • IN JAVA: the blob types are datastore.ShortBlob and datastore.Blob

blobstore

 
© Lynne Grewe