![]() ![]() When tables are created in Big SQL, the Parquet format can be chosen by using the STORED AS PARQUET clause in the CREATE HADOOP TABLE statement as in this example: jsqsh>CREATE HADOOP TABLE inventory ( trans_id int, product varchar(50), trans_dt date ) PARTITIONED BY ( year int) STORED AS PARQUETīy default Big SQL will use SNAPPY compression when writing into Parquet tables. Creating Big SQL Table using Parquet Format The next sections will describe how to enable SNAPPY compression for tables populated in Hive on IBM Open Platform (prior to Big SQL v5) and HortonWorks Data Platform (from Big SQL v5 and going forward). For Hive, by default compression is not enabled, as a result the table could be significantly larger if created and/or populated in Hive. When loading data into Parquet tables Big SQL will use SNAPPY compression by default. Hive tables can also be populated from Hive and then accessed from Big SQL after the catalogs are synced. This means that Big SQL tables can be created and populated in Big SQL or created in Big SQL and populated from Hive. One of the biggest advantages of Big SQL is that Big SQL syncs with the Hive Metastore. Big SQL supports table creation and population from Big SQL as well as from Hive. The distinction of what type of file format is to be used is done during table creation. Read this paper for more information on the different file formats supported by Big SQL. The mapping between an object's MessageInfo.type and its respective Protobuf message type must by extracted from the iWork applications at runtime.Big SQL supports different file formats. Fortunately, all of this information can be recovered from the iWork binaries using proto-dump.Ī full dump of the Protobuf messages can be found here. This information can be recovered by inspecting the TSPRegistry class at runtime.īecause Protobuf is not a self-describing format, applications attempting to understand the payloads must know a great deal about the data types and hierarchy of the objects serialized by iWork. ![]() The iWork applications manually map these integer values to their respective Protobuf message types, and the mappings vary slightly between Keynote, Pages and Numbers. The format of the payload is determined by the type field of the associated MessageInfo message. The ArchiveInfo includes a variable number of MessageInfo messages describing the encoded Payloads that follow, though in practice iWork files seem to only have one payload message per ArchiveInfo. Each object begins with a varint representing the length of the ArchiveInfo message, followed by the ArchiveInfo message itself. The uncompresed IWA contains the Component's objects, serialized consecutively in a Protobuf stream. The 4 byte header is not included in the chunk length. The next three bytes are interpreted as a 24-bit little-endian integer indicating the length of the chunk. The first byte indicates the chunk type, which in practice is always 0 for iWork, indicating a Snappy compressed chunk. The stream is composed of contiguous chunks prefixed by a 4 byte header. In particular, they do not include the required Stream Identifier chunk, and compressed chunks do not include a CRC-32C checksum. IWA files are stored in Snappy's framing format, though they do not adhere rigorously to the spec. Snappy is a compression format created by Google aimed at providing decent compression ratios at high speeds. iwa (iWork Archive) files, a custom format consisting of a Protobuf stream wrapped in a Snappy stream. iwa files are inherently compressed (see Snappy Compression), the zip implementation used for Index.zip could be designed to be minimial and efficient. ![]() iwa files, only the Index.zip must be locked. Saving a document might involve writing out several Components, so instead of coordinating writes to the various individual. One possibility is that Index.zip is used to prevent the syncronization issues that would occur if reading and writing a document involved accessing many small files. The iWork '13 applications contain a separate, more complete zip implementation used for reading and writing iWork '09 documents (which are bundles that have been zipped in their entirety), so I believe the choice to forgo compression for Index.zip is intentional. Simply expanding Index.zip and then recreating it with a standard zip utility will result in a document that iWork refuses to open. It does not support any form of compression or extensions like Zip64. Curiously, the zip implementation iWork uses for this file is extremely limited. ![]()
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