These are all the supported column types in Hive:
BIGDECIMAL(Only available starting with Hive 0.10.0)
BINARY(Only available starting with Hive 0.8.0)
TIMESTAMP(Only available starting with Hive 0.8.0)
STRUCT<col_name : data_type [COMMENT col_comment], ...>
UNIONTYPE<data_type, data_type, ...>
Supports traditional UNIX timestamp with optional nanosecond precision.
Timestamps are interpreted to be timezoneless and stored as an offset from the UNIX epoch. Convenience UDFs for conversion to and from timezones are provided (to_utc_timestamp, from_utc_timestamp).
All existing datetime UDFs (month, day, year, hour, etc.) work with the TIMESTAMP data type.
Union types can at any one point hold exactly one of their specified data types. You can create an instance of this type using the
The first part in the deserialized union is the tag which lets us know which part of the union is being used. In this example
0 means the first data_type from the definition which is an
int and so on.
To create a union you have to provide this tag to the
Integral literals are assumed to be INT by default, unless the number exceeds the range of INT in which case it is interpreted as a BIGINT, or if one of the following postfixes is present on the number.
String literals can be expressed with either single quotes (') or double quotes ("). Hive uses C-style escaping within the strings.
Floating point literals are assumed to be DOUBLE. Scientific notation is not yet supported.
BigDecimal literals provide greater precision and range for floating point numbers than the DOUBLE data type. They are needed for use cases in which the precision of a DOUBLE is insufficient, such as financial applications, and for cases that deal with numbers outside the DOUBLE range (approximately -10308 to 10308) or very close to zero (-10-308 to 10-308). The precision of a BigDecimal is practically unlimited.
For a general discussion of the limits of the DOUBLE data type, see the Wikipedia article Double-precision floating-point format.
You can create a table in Hive that uses the BigDecimal type with the following syntax:
The table decimal_1 is a table having one field of type decimal which is basically a BigDecimal value.
You can read and write values in such a table using either the LazySimpleSerDe or the LazyBinarySerDe. For example:
You can use a cast to convert a BigDecimal value to any other primitive type such as a BOOLEAN. For example:
BigDecimal also supports many mathematical UDFs with the same syntax as used in the case of DOUBLE.
Basic mathematical operations that can use decimal types include:
These rounding functions can also take decimal types:
But these mathematical UDFs are not currently supported:
Power(decimal, n) only supports positive integer values for the exponent n.
Casting is supported between decimal values and integer, double, and so on.
Two new tests have been added as part of the TestCliDriver framework within Hive. They are decimal_1.q and decimal_2.q. Other tests such as udf7.q cover the gamut of UDFs mentioned above.
More tests need to be added that demonstrate failure or when certain types of casts are prevented (for example, casting to date). There is some ambiguity in the round function because the rounding of BigDecimal does not work exactly as the SQL standard, and therefore it has been omitted in the current work.
Missing values are represented by the special value NULL. To import data with NULL fields, check documentation of the SerDe used by the table. (The default Text Format uses LazySimpleSerDe which interprets the string \N as NULL when importing.)