reset()
Here’s how to use reset() function.
cs.reset()
Description:
Reset a cursor by moving it back to the beginning.
Syntax:
cs.reset()
Note:
The function resets a cursor by moving it back to the beginning when it traverses cursor data to the end.
Note: Cursors returned from certain functions are irreversible, including db.cursor@x(), f.cursor@x(), cs.groupx(), cs.sortx(), cs.joinx() and cursor(dfx,…).
Parameter:
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cs |
A cursor |
Return value:
The cursor itself
Example:
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A |
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1 |
=demo.cursor("select * from scores") |
Return retrieved data as a cursor |
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2 |
=A1.fetch() |
Fetch data from the cursor
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3 |
=A1.fetch() |
Return null because A1’s cursor has come to the end of the data |
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4 |
=A1.reset() |
Move the cursor back to the beginning |
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5 |
=A1.fetch() |
Fetch data out of the cursor; returned result is the same as A2 |
Related function:
f.reset()
Description:
Reorganize a composite table and write it to another composite table file.
Syntax:
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Note:
The function rearranges composite table or multi-zone composite table f and writes it to file or homo-names files group f’, with patch tables merged into it. It reorganizes f itself and re-creates the index when f’ is absent. It changes structure of zone tables when f’ is a homo-names files group; parameter x is the zone table expression.
Parameter:
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f |
A composite table file/multi-zone composite table/ |
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f’ |
A composite table file or a homo-name files group |
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x |
Zone table expression |
Option:
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@u |
Write the file as an uncompressed one; perform the write as usual if the parameter is omitted |
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@z |
Write the file as a compressed one; won’t perform compression if the option is absent |
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@r |
Write the file by row; perform the write as usual if the parameter is omitted |
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@c |
Write the file by column |
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@q |
A quick reset |
Return value:
Boolean value
Example:
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A |
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1 |
=file("D:\\test1.ctx") |
An existing composite table file |
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2 |
=A1.reset(file("D:\\e1.ctx")) |
Copy composite table file test1 to e1.ctx |
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3 |
=A1.reset@z(file("D:\\e2.ctx")) |
Copy composite table file test1 as a segmented file |
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4 |
=A1.reset@c(file("D:\\e3.ctx")) |
Copy composite table file test1 as a columwise stored file |
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5 |
=A1.reset@u(file("D:\\e4.ctx")) |
Copy composite table file test1 as an unsegmented file |
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6 |
=A1.reset() |
Clear test1.ctx and re-create index for it |
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7 |
=A1.reset@r(file("D:\\e5.ctx")) |
Copy composite table file test1 as a rowwise stored file |
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8 |
=file("D:\\emp12.ctx") |
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9 |
Open A8’s composite table file and data in its base table is as follows:
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10 |
=create(EID,NAME).record([4,"Emily"]) |
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11 |
=A9.delete(A10) |
Delete A12’s record from A10’s composite table |
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12 |
=A9.close() |
Close the composite table |
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13 |
=A8.reset@q() |
Reset the composite table file |
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14 |
=file("emp.ctx":[2,3]) |
Return a homo-name files group |
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15 |
=file("emCp.ctx":[2,3]) |
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16 |
=A14.reset(A15) |
Reorganize 2.emp.ctx and 3.emp.ctx in A14’s homo-name files group and write them to 2.empCp.ctx and 3.empCp.ctx respectively in a new files group |
T.reset()
Description:
Clear the members of a table sequence.
Syntax:
T.reset()
Note:
The function clears members from table sequence T, but reserves the data structure.
Parameter:
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T |
A table sequence |
Return value:
The empty table sequence T.
Example:
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A |
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1 |
=demo.query("select * from EMPLOYEE") |
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2 |
=A1.reset() |
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