structure

Read(1705) Label: structure,

Here is how use the structure() function.

f.structure()

Description:

Get structure information of a composite table.

Sytnax:

f.structure()

Note:

The function gets composite table f’s structure information, which includes the following contents:

Structure

Description

[field]

A sequence of fields

name

Field name

dim

Whether a field is dimension

type

Data type; enter null if a field isn’t pure

key

Whether a dimension field is the primary key

del

Whether there is a deletion mark

row

Whether row-wise storage is used

zip

Whether data is compressed

seg

Whether data is segmented by the first field

zonex

Zone table expression

Index

 

hash

HASH index length; =0 means an ordered index and null represents a full-text index

[keys]

A sequence of fields on which index is created

[field]

A sequence of fields to which values are attached

where

Filter condition

Pre-aggregation

 

[keys]

Grouping key

[aggr]

Aggregate

name

Field name

exp

Aggregate expression

[attach]

Attached table; fill in this field with nulls if there isn’t any attached table

name

Name

List structures of other composite tables recursively

block

Block size

Parameter:

f

A composite table/multizone composite table/index file/preaggregation file

Option:

@i

Means f is an index file

@c

Means f is a preaggregation file

Return value:

Table sequence

Example:

When f is a composite table:

 

A

 

1

=demo.query("select EID,NAME from employee")

 

2

=demo.cursor("select EID,SALARY from employee")

 

3

=file("str.ctx")

 

4

=A3.create@y(#EID,NAME)

Create a composite table whose key is EID and that is column-oriented and uses compression; block size uses the system default.

5

=A4.append(A1)

 

6

=A4.attach(salary,SALARY)

Add an attached table named salary to the composite table.

7

=A6.append(A2)

 

8

>A5.close()

 

9

=A3.structure()

 

When f is an index file:

 

A

 

1

=file("emp1.ctx")

 

2

=A1.create@y(#EID,NAME,GENDER,DEPT,SALARY)

Create a composite table.

3

=demo.cursor("select  EID,NAME,GENDER,DEPT,SALARY from employee ")

Return a cursor.

4

=A2.append(A3)

Append cursor A3’s data to the composite table.

5

=file("index1")

Return a file object.

6

=A2.index(A5:10,GENDER=="F";EID)

Create a HASH index file of length 10 for the composite table on indexed field EID.

7

=A5.structure@i()

Return structure of index file index1:

 

When f is a preaggregation file:

 

A

 

1

=file("emp1.ctx")

 

2

=A1.create@y(#EID,NAME,GENDER,DEPT,SALARY)

Create a composite table.

3

=demo.cursor("select  EID,NAME,GENDER,DEPT,SALARY from employee ")

Return a cursor.

4

=A2.append(A3)

Append cursor A3’s data to the composite table.

5

=file("cub1")

Return a file object.

6

=A2.cuboid(A5,DEPT;avg(SALARY))

Create a preaggregation file for the composite table.

7

=A5.structure@c()

Return structure of preaggregation file cub1.