attach()

Read(275) Label: attach,

Here’s how to use attach() function.

T.attach(T’)

Description:

Retrieve an attached table from a cluster composite table.

Syntax:

T.attach(T’)

Note:

The function retrieves attached table T’, which should already exist, from cluster composite table T.

Parameters:

T

A cluster composite table

T’

An attached table

Return value:

An attached table

Example:

Here’s composite table emp1.ctx:

 

A

 

1

=file("D:\\emp1.ctx")

 

2

=A1.create(#EID,NAME)

Create the composite table’s base table

3

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

 

4

=A2.append(A3)

Append records to the base table

5

=A2.attach(t1, SURNAME,DEPT )

Add attached table t1 to the base table

6

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

 

7

=A5.append(A6)

Append records to attached table t1

8

=A2.attach(t2,GENDER,SALARY)

Add attached table t2 to the base table

9

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

 

10

=A8.append(A9)

Append records to attached table t2

 

 

A

 

1

=file@0("emp1.ctx",["192.168.0.116:8281","192.168.0.129:8281"])

Generate a duplicate cluster file

2

=A1.create()

Create a duplicate cluster composite table

3

=A2.attach(t1)

Retrieve attached table t1

T.attach( T’,C… )

Description:

Add an attached table to the base table of a composite table.

Synatx:

T.attach(T’,C…)

Note:

The function adds attached table T’ to a composite table’s base table T. A composite table can have one or multiple attached tables. The attached table’s dimensions include the dimensions of its parent table (the base table); its column names should be different from the base table’s column names.

Parameters:

T

A base table

T’

An attached table

C

Attached table column, can be omitted; return an attached table named T’ if it is absent; a C preceded by # is a dimension

Return value:

An attached table

Example:

 

A

 

1

=file("D:/ctb.ctx")

 

2

=A1.create(#k1,v1)

Create the composite table’s base table where k1 is the dimension and v1 is the column

3

=A2.attach(table2,#k2,v2)

Add attached table table2 to A2’s base table; k1 and k2 are the attached table’s dimensions and v1 and v2 are its columns

4

=A2.attach(table3,v3)

Add attached table table3 to A2’s base table; k1 is the attached table’s dimension and v1 and v3 are its columns

ch.attach()

Description:

Attach an operation to a channel.

Syntax:

ch.attach(…)

Note:

The function attaches an operation to channel ch. The sign ~ used in the expression parameter … represents the result of the previous operation performed in the channel.

Parameters:

ch

Channel

An expression of performing an operation over a sequence

Return value:

Channel

Example:

 

A

 

1

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

2

=channel()

Create a channel

3

=A2.select(SALARY>10000)

Attach a ch.select() operation to the channel

4

=A2.attach(~.sort(-SALARY))

Attach a A.sort() operation to the channel

5

=A2.fetch()

Attach ch.fetch() function that gets the final result set to A2’s channel to fetch and store the existing data in the channel

6

=A1.push(A2)

Push the data in A1’s sequence into the channel

7

=A2.result()

Get the result of the last operation performed in the channel