getDataIndex

Retrieves an existing data index for a given table and specified key column(s). It can optionally create the index if it does not already exist.

This method is part of the io.deephaven.engine.table.impl.indexer.DataIndexer class and is typically used via a static import.

Syntax

index = getOrCreateDataIndex(someTable, "KeyColumn1") // Create if missing
index = getDataIndex(someTable, "KeyColumn1", "KeyColumn2") // Retrieve only if exists
index = getOrCreateDataIndex(someTable, "KeyColumn1", "KeyColumn2") // Create if missing

Parameters

Parameter	Type	Description
table	Table	The table from which to retrieve the data index.
createIfAbsent	boolean	If `true`, creates the data index if it doesn't exist. If `false`, returns `null` if the index doesn't exist.
keyColumnNames	String...	The name(s) of the key column(s) defining the index (varargs).
keyColumnNames	String[]	The name(s) of the key column(s) defining the index (array).

Returns

Returns the DataIndex object if found or created. Returns null if createIfAbsent is false and the index does not exist.

Examples

Example 1: Retrieve an index, don't create if absent

import static io.deephaven.engine.table.impl.indexer.DataIndexer.getDataIndex
import static io.deephaven.engine.table.impl.indexer.DataIndexer.getOrCreateDataIndex
import static io.deephaven.engine.table.impl.indexer.DataIndexer.hasDataIndex

// Create a source table
def sourceTable = emptyTable(100).update(
    "Key1 = (int)i % 10",
    "Value = i"
)

// Attempt to get an index on Key1
def indexKey1_noCreate = getDataIndex(sourceTable, "Key1") // Retrieve only if exists
println "Index on Key1 (no create): ${indexKey1_noCreate}"  // Output: null
println "Has index on Key1 after attempt: ${hasDataIndex(sourceTable, "Key1")}" // Output: false

// Now, explicitly create an index on Key1
def actualIndexKey1 = getOrCreateDataIndex(sourceTable, "Key1")

// Attempt to get the index on Key1 again
def indexKey1_exists = getDataIndex(sourceTable, "Key1") // Retrieve only if exists
println "Index on Key1 (exists): ${indexKey1_exists}"  // Output: (DataIndex object)
println "Is indexKey1_exists the same as actualIndexKey1? ${indexKey1_exists == actualIndexKey1}" // Output: true

Example 2: Retrieve an index, create if absent

import static io.deephaven.engine.table.impl.indexer.DataIndexer.getDataIndex
import static io.deephaven.engine.table.impl.indexer.DataIndexer.hasDataIndex

// Create a source table
def sourceTable2 = emptyTable(50).update(
    "Symbol = \"SYM\" + (int)(i % 3)",
    "Price = i * 1.1"
)

// Attempt to get an index on Symbol
println "Has index on Symbol BEFORE: ${hasDataIndex(sourceTable2, "Symbol")}" // Output: false
def indexSymbol_create = getOrCreateDataIndex(sourceTable2, "Symbol") // Create if missing
println "Index on Symbol (create): ${indexSymbol_create}"  // Output: (DataIndex object)
println "Has index on Symbol AFTER: ${hasDataIndex(sourceTable2, "Symbol")}" // Output: true