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125 lines
3.3 KiB
ReStructuredText
125 lines
3.3 KiB
ReStructuredText
.. _ColumnDatum:
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ColumnDatum
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===========
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Since aggregate functions can operate on any data type, we use the ColumnDatum struct to define the input row data. To be type insensiteve, data is stored in type static_any::any.
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To access the data it must be type cast to the correct type using static_any::any::cast().
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Example for int data:
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::
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if (valIn.compatible(intTypeId)
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int myint = valIn.cast<int>();
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For multi-paramter aggregations (not available in Columnstore 1.1), the colsIn array of next_value() contains the ordered set of row parameters.
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For char, varchar, text, varbinary and blob types, columnData will be std::string.
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The intTypeId above is one of a set of "static const static_any::any&" provided in mcsv1_UDAF for your use to figure out which type of data was actually sent. See the MEDIAN example for how these might be used to accept any numeric data type.
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The provided values are:
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* charTypeId
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* scharTypeId
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* shortTypeId
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* intTypeId
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* longTypeId
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* llTypeId
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* ucharTypeId
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* ushortTypeId
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* uintTypeId
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* ulongTypeId
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* ullTypeId
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* floatTypeId
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* doubleTypeId
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* strTypeId
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.. rubric:: The ColumnDatum members.
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.. c:member:: CalpontSystemCatalog::ColDataType dataType;
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ColDataType is defined in calpontsystemcatalog.h and can be any of the following:
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.. _coldatatype:
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.. list-table:: ColDataType
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:widths: 10 50
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:header-rows: 1
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* - Data Type
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- Usage
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* - BIT
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- Represents a binary 1 or 0. Stored in a single byte.
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* - TINYINT
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- A signed one byte integer
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* - CHAR
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- A signed one byte integer or an ascii char
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* - SMALLINT
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- A signed two byte integer
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* - DECIMAL
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- A Columnstore Decimal value. This is stored in the smallest integer type field that will hold the required precision.
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* - MEDINT
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- A signed four byte integer
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* - INT
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- A signed four byte integer
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* - FLOAT
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- A floating point number. Represented as a C++ float type.
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* - DATE
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- A Columnstore date stored as a four byte unsigned integer.
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* - BIGINT
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- A signed eight byte integer
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* - DOUBLE
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- A floating point number. Represented as a C++ double type.
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* - DATETIME
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- A Columnstore date-time stored as an eight byte unsigned integer.
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* - TIME
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- A Columnstore time stored as an eight byte unsigned integer.
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* - VARCHAR
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- A mariadb variable length string. Represented a std::string
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* - VARBINARY
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- A mariadb variable length binary. Represented a std::string that may contain embedded '0's
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* - CLOB
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- Has not been verified for use in UDAF
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* - BLOB
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- Has not been verified for use in UDAF
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* - UTINYINT
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- An unsigned one byte integer
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* - USMALLINT
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- An unsigned two byte integer
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* - UDECIMAL
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- DECIMAL, but no negative values allowed.
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* - UMEDINT
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- An unsigned four byte integer
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* - UINT
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- An unsigned four byte integer
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* - UFLOAT
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- FLOAT, but no negative values allowed.
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* - UBIGINT
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- An unsigned eight byte integer
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* - UDOUBLE
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- DOUBLE, but no negative values allowed.
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* - TEXT
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- Has not been verified for use in UDAF
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.. c:member:: static_any::any columnData;
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Holds the value for this column in this row.
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.. c:member:: uint32_t scale;
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If dataType is a DECIMAL type
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.. c:member:: uint32_t precision;
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If dataType is a DECIMAL type
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.. c:function:: ColumnDatum()
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Sets defaults.
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