Data Type Conversions from Hive to Vertica

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Hive uses the SerDe interface for IO. The interface handles both serialization and deserialization and also interpreting the results of serialization as individual fields for processing. Anyone can write their own SerDe for their own data formats. The Hive SerDe library is in org. For Hive releases prior to 0. So the engine first initializes the UDF by calling this method. Output is analogous to input. The engine passes the deserialized Object representing a record and the corresponding ObjectInspector to Serde.

In this context serialization means converting the record object to an object of the type expected by the OutputFormat which will be used to perform the write. To hive ser de binary options this conversion, the serialize method can make use of the passed ObjectInspector to get the individual fields in the record in order to convert the record to the appropriate type. In short, Hive will automatically convert objects so that Integer will be converted to IntWritable and vice versa if needed.

SerDe can serialize an object that is created by another serde, using ObjectInspector. I asked about them in a comment on HIVE If they aren't escape characters, could they be leftovers from a previous formatting style?

Hive ser de binary options you review it? Space shortcuts How-to articles. I noticed that there are '! Permalink Feb 22, Delete comments. The exclamation marks also hive ser de binary options in two sections of the Developer Guide: Permalink Feb 23, Delete comments.

Yes, they are artifacts of the old MoinMoin Wiki syntax and can be removed. And they're gone, gone, solid gone. Permalink Feb 25, Delete comments. Permalink Dec 15, Delete comments. Hive ser de binary options Jan 06, Delete comments. Permalink Jan 07, Delete comments. Permalink Mar 19, Delete comments. Powered by Atlassian Confluence 5. Report a bug Atlassian News Atlassian.

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Creating an external file format is a prerequisite for creating an External Table. By creating an External File Format, you specify the actual layout of the data referenced by an external table. This option requires Hive version 0. Note, the SerDe method is case-sensitive. The field terminator specifies one or more characters that mark the end of each field column in the text-delimited file. For guaranteed support, we recommend using one or more ascii characters.

The string delimiter is one or more characters in length and is enclosed with single quotes. The default is the empty string "". This parameter can take values If the value is set to two, the first row in every file header row is skipped when the data is loaded.

When this option is used for export, rows are added to the data to make sure the file can be read with no data loss. If the source file uses default datetime formats, this option isn't necessary. Only one custom datetime format is allowed per file.

You can't specify more than one custom datetime formats per file. However, you can use more than one datetime formats if each one is the default format for its respective data type in the external table definition. PolyBase only uses the custom date format for importing the data. It doesn't use the custom format for writing data to an external file. Year, month, and day can have a variety of formats and orders. The table shows only the ymd format. Month can have one or two digits, or three characters.

Day can have one or two digits. Year can have two or four digits. For simplicity, the table uses only the ' — ' separator. To specify the month as text, use three or more characters.

Months with one or two characters are interpreted as a number. The letters 'tt' designate [AM PM am pm]. AM is the default. When 'tt' is specified, the hour value hh must be in the range of 0 to TRUE When retrieving data from the text file, store each missing value by using the default value for the data type of the corresponding column in the external table definition.

For example, replace a missing value with:. To work properly, Gzip compressed files must have the ". It is server-scoped in Parallel Data Warehouse. When the data is stored in one of the compressed formats, PolyBase first decompresses the data before returning the data records. These delimiters are not user-configurable. The combinations of supported SerDe methods with RCFiles, and the supported data compression methods are listed previously in this article. Not all combinations are supported.

The maximum number of concurrent PolyBase queries is When 32 concurrent queries are running, each query can read a maximum of 33, files from the external file location.

The root folder and each subfolder also count as a file. If the degree of concurrency is less than 32, the external file location can contain more than 33, files. Because of the limitation on number of files in the external table, we recommend storing less than 30, files in the root and subfolders of the external file location.

Also, we recommend keeping the number of subfolders under the root directory to a small number. When too many files are referenced, a Java Virtual Machine out-of-memory exception might occur. Using compressed files always comes with the tradeoff between transferring less data between the external data source and SQL Server while increasing the CPU usage to compress and decompress the data. Gzip compressed text files are not splittable.

To improve performance for Gzip compressed text files, we recommend generating multiple files that are all stored in the same directory within the external data source. This file structure allows PolyBase to read and decompress the data faster by using multiple reader and decompression processes.

The ideal number of compressed files is the maximum number of data reader processes per compute node. This example creates an external file format named textdelimited1 for a text-delimited file. The text file is also compressed with the Gzip codec. For a delimited text file, the data compression method can either be the default Codec, 'org.

DefaultCodec', or the Gzip Codec, 'org. It also specifies to use the Default Codec for the data compression method. This example creates an external file format for an ORC file that compresses the data with the org. SnappyCodec data compression method. This example creates an external file format for a Parquet file that compresses the data with the org.

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PolyBase supports the following file formats: Notes about the table: Milliseconds fffffff are not required. Am, pm tt isn't required. The default is AM. No time element is included.

See the description in the previous row. All supported date formats: To separate time values, use the ': Letters enclosed in square brackets are optional. For example, replace a missing value with: Empty string "" if the column is a string column. The format options are all optional and only apply to delimited text files.

Performance Using compressed files always comes with the tradeoff between transferring less data between the external data source and SQL Server while increasing the CPU usage to compress and decompress the data.

In addition to year, month and day, this date format includes hours, minutes, seconds, and 3 digits for milliseconds. In addition to year, month and day, this date format includes hours, minutes, seconds, 3 digits for milliseconds, and AM, am, PM, or pm. In addition to year, month, and day, this date format includes hours, minutes, no seconds, and AM, am, PM, or pm. Year, month, and day. In addition to year, month, and day, this date format includes hours, minutes, seconds, and 7 digits for milliseconds.

In addition to year, month, and day, this date format includes hours, minutes, seconds, 7 digits for milliseconds, and AM, am, PM, or pm. In addition to year, month, and day, this date format includes hours, minutes, seconds, 7 digits for milliseconds, AM, am, PM, or pm , and the timezone offset.