Deleting Rows from the Store

Deleting Rows from the Store
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Using multi_delete()

You delete a single row from the store using the Store.delete() method. Rows are deleted based on a dictionary that defines the full primary key for the row that you want to delete. You can also require a row to match a specified version before it will be deleted. To do this, use the Store.delete_if_version() method. Versions are described in Using Row Versions.

When you delete a row, you must handle the same errors as occur when you perform any write operation on the store. See Write Exceptions for a high-level description of these errors.

try:
    # To delete a table row, just include a dictionary
    # that contains all the fields needed to create
    # the primary key.
    primary_key_d = {"item" : "bolts"}
    ret = store.delete("myTable", primary_key_d)
    if ret[0]:
        logging.debug("Row deletion succeeded")
    else:
        logging.debug("Row deletion failed.")
except IllegalArgumentException, iae:
    logging.error("Row deletion failed.")
    logging.error(iae.message)

Using multi_delete()

You can delete multiple rows at once in a single atomic operation, so long as they all share the shard key values. Recall that shard keys are at least a subset of your primary keys. The result is that you use a partial primary key (which happens to be a shard key) to perform a multi-delete.

To delete multiple rows at once, use the Store.multi_delete() method.

For example, suppose you created a table like this:

CREATE TABLE myTable (
    itemType STRING,
    itemCategory STRING,
    itemClass STRING,
    itemColor STRING,
    itemSize STRING,
    price FLOAT,
    inventoryCount INTEGER,
    PRIMARY KEY (SHARD(itemType, itemCategory, itemClass), itemColor,
    itemSize)
)

With tables containing data like this:

Row 1:

itemType: Hats

itemCategory: baseball

itemClass: longbill

itemColor: red

itemSize: small

price: 12.07

inventoryCount: 127

Row 2:

itemType: Hats

itemCategory: baseball

itemClass: longbill

itemColor: red

itemSize: medium

price: 13.07

inventoryCount: 201

Row 3:

itemType: Hats

itemCategory: baseball

itemClass: longbill

itemColor: red

itemSize: large

price: 14.07

inventoryCount: 39

Then in this case, you can delete all the rows sharing the partial primary key Hats, baseball, longbill as follows:

try:
    primary_key_d = {'itemType'     : 'Hats',
                     'itemCategory' : 'baseball',
                     'itemClass'    : 'longbill'}

    ret = store.multi_delete("myTable", primary_key_d)
    if ret > 0:
        logging.debug("%s rows deleted" % ret)
    else:
        logging.debug("No rows deleted.")
except IllegalArgumentException, iae:
    logging.error("Row deletion failed.")
    logging.error(iae.message)

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