sortx()

Read(2427) Label: sortx,

Here’s how to use sortx() function.

ch.sortx()

Description:

Sort records in a channel.

Syntax:

ch.sortx(x,…)

Note:

The function sorts records in channel ch by expression x,… and returns the sorted records as a channel. This is a function for directly getting a result set from the channel.

Parameter:

ch

Channel

x

An expression, according to which the records in a given channel is sorted in ascending order

Return value:

Channel

Example:

 

A

 

1

=demo.cursor("select EID,NAME,DEPT,SALARY from EMPLOYEE order by EID desc")

Return a cursor with desired records.

2

=channel()

Create a channel.

3

=A2.sortx(SALARY,EID)

Sort records in the channel by SALARY field and EID field.

4

=A1.push(A2)

Push data in A1’s cursor into the channel

5

=A1.fetch()

Fetch data from A1’s cursor.

6

=A2.result()

Return result as a cursor.

7

=A6.fetch()

cs.sortx()

Description:

Sort data of a cursor.

Syntax:

cs.sortx(x,…;n)

Note:

The function sorts cursor cs by expression x, and returns result as a cursor. The cursor the function returns is irreversible.

Parameter:

cs

A cursor

x

An expression to sort members of cursor cs in ascending order

n

Number of buffer rows; if the number of groups reaches n, write the grouping result to a temporary file; its value will be n times of the default if it is less than 1; by default, esProc will auto-compute the value

Option:

@0

Put records with null values at the end; @0 and @n can’t work together

@n

It can only be used to make the calculation faster when the value of expression x is a positive integer over which group of records can be directly numbered. @0 and @n can’t work together

@g

Treat parameter n as the segmentation expression by which records are first segmented and then grouped and sorted

Return value:

Cursor

Example:

 

A

 

1

=demo.cursor("select NAME,BIRTHDAY,HIREDATE from Employee")

Return retrieved data as a cursor.

2

=A1.sortx(BIRTHDAY)

Sort the cursor’s BIRTHDAY field.

3

=A2.fetch()

Retrieve data from cursor A2.

4

=demo.cursor("select * from DEPT")

Return retrieved data as a cursor.

5

=A4.sortx@0(FATHER).fetch()

Sort records in the cursor by FATHER field and put the one with null value at the end.

6

=A4.sortx@g(DEPTID;FATHER==12).fetch()

Group records according to whether FATHER value is 12 and then sort each group by DEPTID.

7

=A1.sortx(BIRTHDAY;2)

Sort BIRTHDAY field in the cursor; since data is divided into two groups to be processed, write the grouping result to a temporary file.

8

=demo.cursor("select * from SCORES")

 

9

=A8.sortx@n(SCORE).fetch()

The result of fetching SCORE values are integers; here @n option is used to speed up the sorting.

Related function:

cs.fetch()

db.cursor()

cs.sortx()

Description:

Sort a cluster cursor.

Syntax:

cs.sortx(x,…;n)

Note:

The function sorts cluster cursor cs by expression x and returns a cluster cursor.

Option:

@c

Won’t merge result sets returned by the nodes but return a cluster cursor segmented in the same way

Parameter:

cs

A cluster cursor

x

An expression by which records in a specified cluster cursor are sorted in ascending order

n

 

Number of buffer rows; if the number of groups reaches n, write the grouping result to a temporary file; its value will be n times of the default if it is less than 1; by default, esProc will auto-compute the value

Return value:

A cluster cursor

Example:

 

A

 

1

[192.168.0.110:8281,192.168.18.143:8281]

 

2

=file("emp.ctx", A1)

 

3

=A2.open()

Open a cluster composite table file.

4

=A3.cursor()

Return a cluster cursor.

5

=A4.sortx(EID)

Sort A4’s cluster cursor by EID and return result also as a cluster cursor.

f.sortx()

Description:

Sort a bin file or a sequence of bin files and generate a new bin file.

Syntax:

f.sortx(Fi,…;fn)

Sort a bin file according to field Fi and generate a new bin file

[fi,…].sortx(Fi,…;fn)

Sort a sequence of bin files according to field Fi and generate a new bin file; perform a simple concatenation when parameter Fi is absent

Note:

The function sorts bin file f or a sequence of bin files [fi,…] by certain field Fi , generates a new bin file fn and return non-null if the operation succeeds.

Parameter:

f

A bin file object

[fi,…]

A sequence of bin files of same structure

Fi

Name(s) of f field(s) by which the file is sorted

fn

Bin file object(s); generate a temporary file and return its cursor when this parameter is absent

Option:

@z

Sort in descending order; default is ascending

Return value:

Boolean/cursor

Example:

Sort a bin file:

 

A

 

1

=file("PERFORMANCE.btx")

A bin file object; its content is as follows:

2

=file("PER-cp.btx")

Specify a bin file object.

3

=A1.sortx(BONUS;A2)

Sort PERFORMANCE.btx by BONUS field and generate a new bin file PER-cp.btx, whose content is as follows:

4

=A1.sortx(BONUS)

As parameter fn is absent, generate a temporary file in the temporary directory and return a cursor, whose content is same as that in A3.

5

=A1.sortx@z(BONUS)

Sort by BONUS field in descending order and return a cursor whose content is as follows:

 

Sort a sequence of bin files:

 

A

 

1

=file("f_emp.btx")

A bin file object; its content is as follows:

2

=file("m_emp.btx")

A bin file object; its content is as follows:

3

=file("emp_all.btx")

 

4

=[A1,A2].sortx(SALARY,EID;A3)

Sort f_emp.btx and m_emp.btx by SALARY and EID fields and generate a new bin file emp_all.btx, whose content is as follows:

5

=[A1,A2].sortx(SALARY)

As parameter fn is absent, return a cursor.

 

Perform a simple concatenation on a sequence of bine files when parameter Fi is absent:

 

A

 

1

=file("f_emp.btx")

A bin file object whose content is as follows:

2

=file("m_emp.btx")

A bin file object whose content is as follows:

3

=file("emp_gb.btx")

 

4

=[A1,A2].sortx(;A3)

Concatenate f_emp.btx and m_emp.btx and generate a new bin file emp_gb.btx whose content is as follows: