Table

com.apama.memorystore
Event Table

Represents a collection of rows in a store, with a defined schema.

A table consists of a series of rows, each identified by a key and containing other values with names and types according to the table's Schema.

A table typically resides in memory, you can also store it on disk.

See Also:: com.apama.memorystore.Store.open() - Tables exist within a named Store, which is used to create and open tables.

Action summary
`com.apama.memorystore.Row`	`add(string key)` Add the table Row with the specified key.
`com.apama.memorystore.Iterator`	`begin()` Return an iterator to the beginning of the Table.
`void`	`clear()` Remove all rows from the table.
`integer`	`enqueueColumn(string fieldName)` Send an event for each row in the table, taken by parsing the string data in the specified table field/column as an event string.
`com.apama.memorystore.Row`	`get(string key)` Get the table Row with the specified key.
`integer`	`getFieldIndex(string fieldName)` Return the index of a field.
`sequence<string>`	`getKeys()` Returns a sequence that contains the keys for all the rows in this table.
`string`	`getStoreName()` Get the name of the Store that contains this table.
`string`	`getTableName()` Get the name of this Table.
`boolean`	`hasKey(string key)` Indicate whether or not a row with the specified key is present in the table.
`void`	`mutate(string key, action<com.apama.memorystore.Row> a)` Change the row with the specified key by applying an action to it.
`void`	`mutateAll(action<com.apama.memorystore.Row> a)` Mutate all rows in the Table by applying the specified action.
`integer`	`persist()` Persist this table's committed changes back to stable storage, asynchronously.
`void`	`remove(string key)` Remove the specified row from the table.

Action detail

add

com.apama.memorystore.Row add(string key)

Add the table Row with the specified key.

Parameters:: key - The name/key uniquely identifying the row.

Returns:: An empty Row event.

begin

com.apama.memorystore.Iterator begin()

Return an iterator to the beginning of the Table.

clear

void clear()

Remove all rows from the table.

enqueueColumn

integer enqueueColumn(string fieldName)

Send an event for each row in the table, taken by parsing the string data in the specified table field/column as an event string.

The field must be of string type, and its value for every row should be an Apama event string, in the same form that you would send to the Correlator (e.g. "mypackage.MyEvent(123, [false,true])")

Parameters:: fieldName - The name of the table field whose values are event strings that should be sent.

Returns:: The unique identifier for this operation, which will be included in the Finished event sent after the column data for the last row has been sent.

See Also:: com.apama.memorystore.Finished - A Finished event will be sent when this asynchronous operation has completed.

get

com.apama.memorystore.Row get(string key)

Get the table Row with the specified key.

If there is no row with the specified key, this action returns without error, with a Row event that contains default values for the fields in the row. A call to the Row.inTable() action returns false.

Parameters:: key - The name/key uniquely identifying the row.

Returns:: A Row event representing an atomic snapshot of the committed data in the table when the action was called.

getFieldIndex

integer getFieldIndex(string fieldName)

Return the index of a field.

Returns what position in the Schema the specified field appears at. If a name that is not in Schema fieldName is passed in, the monitor instance will be terminated with an error.

Using this action is more efficient that getting the same information by using indexOf on the Schema.fields sequence.

Parameters:: fieldName - A field name that exists in this table's Schema.

getKeys

sequence<string> getKeys()

Returns a sequence that contains the keys for all the rows in this table.

The keys are in an arbitrary order.

getStoreName

string getStoreName()

Get the name of the Store that contains this table.

getTableName

string getTableName()

Get the name of this Table.

hasKey

boolean hasKey(string key)

Indicate whether or not a row with the specified key is present in the table.

t.hasKey("foo") is a more efficient alternative to t.get("foo").inTable()

Parameters:: key - The name/key uniquely identifying the row.

mutate

void mutate(string key, action<com.apama.memorystore.Row> a)

Change the row with the specified key by applying an action to it.

It is possible for another context to commit changes to this row between the time mutate() obtains a Row event to represent the row and the time mutate() tries to commit the changes that result from executing the specified action. In this situation, the MemoryStore automatically calls the specified action again on the most recently committed row content; therefore mutation actions must be designed to cope with being called repeatedly without causing unwanted side effects.

Parameters:: key; a - An action that (idempotently) performs the desired change to the row.

mutateAll

void mutateAll(action<com.apama.memorystore.Row> a)

Mutate all rows in the Table by applying the specified action.

This can temporarily consume a lot of memory when called on a relatively large table because the Correlator does no garbage collection until action execution is complete. A few thousand rows are unlikely to present a problem. Beyond that, it depends on how many fields are in each row, how many rows are in the table, and how much RAM is available.

Parameters:: a - An action that performs the desired change to each row in the table.

persist

integer persist()

Persist this table's committed changes back to stable storage, asynchronously.

Note that any local changes to a Row that were not committed will not be written to disk (see Row#commit()).

Only on-disk persistent stores can be persisted using this action.

Returns:: The unique identifier for this operation, which will be included in the Finished event sent after the operation is complete.

See Also:: com.apama.memorystore.Finished - A Finished event will be sent when this asynchronous operation has completed.

remove

void remove(string key)

Remove the specified row from the table.

If the row does not exist, this action does nothing.

Parameters:: key - The name/key uniquely identifying the row.

com.apama.memorystoreEvent Table

add