Manually creating tables and columns

Deephaven TableTools contains many methods for creating and modifying tables. By default, all methods of TableTools are statically imported into each Groovy session, making an import unnecessary. In Python, the TableTools methods are in the deephaven.TableTools package and must be imported before they are used.

Note

See: TableTools JavaDocs and TableTools PyDocs

Some of these functions follow.

Manually creating tables

emptyTable(numRows) - Creates an empty table with the number of specified rows, but no columns. Once created, users can update the table and add columns and other useful data.

For example:

empty = emptyTable(10).update("Column = i")

from deephaven.TableTools import emptyTable

empty = emptyTable(10).update("Column = i")

emptyTable(int size, TableDefinition tableDefinition)- Creates an empty table with size rows, and column names and types from tableDefinition.
newTable(ColumnHolder... columns) - Creates a new in-memory table based on arrays, creating one column per array you pass in.

The following example starts by defining four arrays of data. These arrays are then passed into the column creation methods (col(), intCol(), doubleCol(), and charCol()), which take a name and an array of data, and create a ColumnHolder object that can be added to a table:

myStrings = ["Str1", "Str2", "Str3", "Str4"] as String[]
myInts = [1, 2, 4, 8] as int[]
myDoubles = [1.0, 2.0, 4.0, 8.0] as double[]
myCharacters = ['A', 'B', 'C', 'D'] as char[]

myTable = newTable(
        col("StringColumn", myStrings),
        intCol("IntegerColumn", myInts),
        doubleCol("Decimals", myDoubles),
        charCol("Characters" , myCharacters)
)

from deephaven import *

myStrings = ["Str1", "Str2", "Str3", "Str4"]
myInts = [1, 2, 4, 8]
myDoubles = [1.0, 2.0, 4.0, 8.0]
myCharacters = ['A', 'B', 'C', 'D']

myTable = ttools.newTable( \
    ttools.col("StringColumn", myStrings), \
    ttools.intCol("IntegerColumn", myInts), \
    ttools.doubleCol("Decimals", myDoubles), \
    ttools.charCol("Characters" , myCharacters) \
    )

Tip

We recommend using newTable for small static tables, and emptyTable when using formulas:

For example:

x = newTable(intCol("X", 42))

is much better than

y = emptyTable(1).view("X=42")

Manually Creating Columns

ColumnHolder<T> col(String name, T... values) - Creates a new data column.
Users may want to create columns for a new table out of arrays. Two examples follow:

myStrings = ["Str1", "Str2", "Str3", "Str4"] as String[]
myInts = [1, 2, 4, 8] as int[]
myDoubles = [1.0, 2.0, 4.0, 8.0] as double[]
myCharacters = ['A', 'B', 'C', 'D'] as char[]

myTable = newTable(
        stringCol("StringColumn", myStrings),
        intCol("IntegerColumn", myInts),
        doubleCol("Decimals", myDoubles),
        charCol("Characters" , myCharacters)
)

from deephaven import *
# deephaven.TableTools module imported as as ttools

myTable1 = ttools.newTable(
    ttools.stringCol("StringColumn", "Str1", "Str2", "Str3", "Str4"),
    ttools.intCol("IntegerColumn", 1, 2, 4, 8),
    ttools.doubleCol("DoubleColumn", 1.0, 2.0, 4.0, 8.0),
    ttools.charCol("CharColumn", "A", "B", "C", "D"))
myTable2 = ttools.newTable(
    ttools.stringCol("StringColumn", ["Str1", "Str2", "Str3", "Str4"]),
    ttools.intCol("IntegerColumn", [1, 2, 4, 8]),
    ttools.doubleCol("DoubleColumn", [1.0, 2.0, 4.0, 8.0]),
    ttools.charCol("CharColumn", ["A", "B", "C", "D"]))

Each line of the query specifies the data type for the column, its name, and the data for that column in the form of an array. In the Groovy script, each array is first assigned to a variable, which is then included in the query that generates the new table.

import com.illumon.iris.db.v2.InMemoryTable

Object columnData = new Object[2]
columnNames = ["OrderType","OrderName"] as String[]
columnData[0] = ['0','1','2','3'] as byte[]
columnData[1] = ["Unknown","Market","Limit","Peg"] as String[]
OrderTypeCodes = new InMemoryTable(columnNames, columnData)

from deephaven import *

InMemoryTable = jpy.get_type("com.illumon.iris.db.v2.InMemoryTable")
columnNames = ["OrderType","OrderName"]
columnData = [
  jpy.array("byte",[0,1,2,3]),
  jpy.array("java.lang.String",["Unknown","Market","Limit","Peg"]),
]
orderTypeCodes = InMemoryTable(columnNames,columnData)

To add a new column to a table definition, use addColumns() from the TableManagementTools class.

Note

See: TableManagementTools JavaDocs and TableManagementTools PyDocs.

Note