memory()
Here’s how to use memory() function.
cs.memory( K,… )
Generate an in-memory table from a cursor.
Syntax:
cs.memory(K,…)
Note:
The function generates an in-memory table, whose key is K, from a cursor. When parameter K is absent, the newly-generated in-memory table will inherit the cursor’s key.
Parameters:
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K |
The key |
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cs |
A cursor |
Options:
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@p |
Group the would-be in-memory table by the first field, which must be ordered; when the first field is already segmented and the to-be-retrieved field, the result table will inherit the segmentation |
Return value:
An in-memory table
Example:
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A |
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1 |
=demo.cursor("select EID,NAME,GENDER,SALARY from EMPLOYEE where EID<10") |
Return the cursor with retrieved data |
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2 |
=A1.memory(EID) |
Return an in-memory table whose key is EID
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3 |
=demo.cursor("select EID,NAME,GENDER,SALARY from EMPLOYEE where EID<10") |
Generate a compressed in-memory table to save space |
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4 |
=A3.memory@p(EID) |
Use @p option to group the would-be in-memory table by the first field |
cs.memory( K,… )
Description:
Generate a cluster in-memory table from a cluster cursor.
Syntax:
cs.memory(K,…)
Note:
According to cluster cursor cs, the function generates a cluster in-memory table that distributed the same way as cs and whose key is K. If cs is a cluster multicursor, load a series of cursors in order.
Parameters:
|
K |
The key; can be omitted |
|
cs |
A cluster cursor |
Return value:
A cluster in-memory table
Example:
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A |
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1 |
=file("test0.ctx","169.254.121.62:8281") |
Open a cluster file |
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2 |
=A1.open() |
Open a cluster table |
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3 |
=A2.attach(table) |
Retrieve cluster table table |
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4 |
=A3.cursor(NAME,GENDER;EID<6) |
Get NAME field and GENDER field where EID<6 from cluster table table and return them as a cursor |
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5 |
=A4.memory(GENDER) |
Generate a cluster in-memory table whose key is GENDER from a cluster cursor |
memory( h,V )
Description:
Generate a cluster in-memory table from a local in-memory table.
Syntax:
memory(h,V)
Note:
The function generates a cluster in-memory table from local in-memory table V, which is stored in a global variable, held in node sequence h.
Parameters:
|
h |
A node sequence |
|
V |
An in-memory table’s global variable |
Return value:
A cluster in-memory table
Example:
Suppose the global variable arg1 is already assigned value using env(v, data) in the initiation script init.dfx:
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A |
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1 |
=memory(["192.168.31.72:8281","192.168.31.72:8291"],arg1) |
Generate a cluster in-memory table from the local in-memory table arg1 |
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2 |
=A1.cursor().fetch() |
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T.memory( C,…;w )
Description:
Generate an in-memory table from an entity table.
Syntax:
T.memory(C,…;w)
Note:
The function filters entity table T according to filtering condition w and imports the data into the memory to generate an in-memory table containing column C. we can handle an in-memory table as we do to a table sequence. When parameter C,… is absent but parameter w is present, the semicolon before w can’t be omitted. If a column C is preceded by # in the entity table, column C will be the key of in-memory table T. Use null to record a C value if it does not exist in T. The in-memory table inherits the entity table’s key if you don’t set a key for it.
Parameters:
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C |
A column name; import all columns when the parameter is omitted |
|
w |
Filtering condition; won’t perform filtering when the parameter is omitted |
|
T |
An entity table in a composite table |
Options:
|
@p |
Group the would-be in-memory table by the first field, which must be ordered; when the first field is already segmented and the to-be-retrieved field, the result table will inherit the segmentation |
Return value:
An in-memory table
Example:
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A |
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1 |
=file("D:\\employees.ctx") |
employees is an existing composite table file |
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2 |
=A1.open() |
Open the composite table |
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3 |
=A2.attach(t1) |
Return the composite table’s attached table t1 |
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4 |
=A2.memory() |
Generate an in-memory table using all columns of the base table
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5 |
=A2.memory(EID,Dept,Name;EID<5) |
Get some columns where EID<5 from the base table to generate an in-memory table
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6 |
=A3.memory() |
Get all columns from the attached table to generate an in-memory table
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7 |
=file("emp.ctx").open() |
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8 |
=A7.memory@p(EID2,NAME,GENDER;GENDER=="M") |
Use @p option to group the would-be in-memory table by the first field |
T.memory( C,…;w )
Description:
Generate a cluster in-memory table from a cluster entity table.
Syntax:
T.memory(C,…;w)
Note:
The function generates a cluster in-memory table, which inherits the zone table expression, from a cluster entity table T, which must have at least one dimension that is used to segment T and facilitates the segmentation. Clear a node’s memory at exit; will perform auto-clear when timeout occurs.
Parameters:
|
C |
A column name; import all columns when the parameter is omitted |
|
w |
Filtering condition; won’t perform filtering when the parameter is omitted |
|
T |
A cluster composite table’s entity table with dimensions |
Return value:
A cluster in-memory table object
Example:
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A |
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1 |
=file("emp1.ctx",["192.168.0.116:8281","192.168.0.129:8281"]) |
Open a cluster file |
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2 |
=A1.open() |
Generate a cluster table |
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3 |
=A2.attach(t1) |
Get cluster table t1 |
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4 |
=A3.memory(NAME,GENDER;EID<5) |
Get columns NAME and GENDER with EID being less than 5 from t1 to generate an in-memory table |