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Parent class

NdbDictionary

Child classes

None

Description

Each instance ofColumn is characterized by its type, which is determined by a number of type specifiers:

• Built-in type

• Array length or maximum length

• Precision and scale (currently not in use)

• Character set (applicable only to columns using string data types)

• Inline and part sizes (applicable only to blob columns)

These types in general correspond to MySQL data types and their variants. The data formats are same as in MySQL. The NDB API provides no support for constructing such formats; however, they are checked by theNDB kernel.

Methods

The following table lists the public methods of this class and the purpose or use of each method:

Table 2.6 Column class methods and descriptions

Method	Description
Column()	Class constructor; there is also a copy constructor
~Column()	Class destructor
equal()	ComparesColumn objects
getArrayType()	Gets the column's array type
getAutoIncrement()	Shows whether the column is auto-incrementing
getCharset()	Get the character set used by a string (text) column (not applicable to columns not storing character data)
getColumnNo()	Gets the column number
getDefaultValue()	Returns the column's default value
getInlineSize()	Gets the inline size of a blob column (not applicable to other column types)
getLength()	Gets the column's length
getName()	Gets the name of the column
getNullable()	Checks whether the column can be set toNULL
getPartitionKey()	Checks whether the column is part of the table's partitioning key
getPartSize()	Gets the part size of a blob column (not applicable to other column types)
getPrecision()	Gets the column's precision (used for decimal types only)
getPrimaryKey()	Check whether the column is part of the table's primary key
getScale()	Gets the column's scale (used for decimal types only)
getSize()	Gets the size of an element
getSizeInBytesForRecord()	Gets the space required for a column byNdbRecord, according to the column's type (added in NDB 7.4.7)
getStripeSize()	Gets a BLOB column's stripe size (not applicable to other column types)
getStorageType()	Gets the storage type used by this column
getType()	Gets the column's type (Type value)
setArrayType()	Sets the column'sArrayType
setAutoIncrement()	Sets the column's auto-increment flag
setAutoIncrementInitialValue()	Sets an auto-incrementing column's starting value
setCharset()	Sets the character set used by a column containing character data (not applicable to nontextual columns)
setDefaultValue()	Sets the column's default value
setInlineSize()	Sets the inline size for a blob column (not applicable to columns not of blob types)
setLength()	Sets the column's length
setName()	Sets the column's name
setNullable()	Toggles the column's nullability
setPartitionKey()	Determines whether the column is part of the table's partitioning key
setPartSize()	Sets the part size for a blob column (not applicable to columns not of blob types)
setPrecision()	Sets the column's precision (used for decimal types only)
setPrimaryKey()	Determines whether the column is part of the primary key
setScale()	Sets the column's scale (used for decimal types only)
setStorageType()	Sets the storage type to be used by this column
setStripeSize()	Sets the stripe size for a blob column (not applicable to columns not of blob types)
setType()	Sets the column'sType

Types

These are the public types of theColumn class:

Table 2.7 Column class types and descriptionse.

Type	Description
ArrayType	Specifies the column's internal storage format
StorageType	Determines whether the column is stored in memory or on disk
Type	The column's data type.NDB columns have the same data types as found in MySQL

Columns created using this class cannot be seen by the MySQL Server. This means that they cannot be accessed by MySQL clients, and that they cannot be replicated. For these reasons, it is often preferable to avoid working with them.

Abstract

This section provides information about theArrayType data type, which represents a column's internal attribute format.

Description

The attribute storage format can be either fixed or variable.

Enumeration values

Possible values are shown, along with descriptions, in the following table:

Table 2.8 Column object ArrayType data type values and descriptions

Name	Description
ArrayTypeFixed	stored as a fixed number of bytes
ArrayTypeShortVar	stored as a variable number of bytes; uses 1 byte overhead
ArrayTypeMediumVar	stored as a variable number of bytes; uses 2 bytes overhead

Description

You can create a newColumn or copy an existing one using the class constructor.

AColumn created using the NDB API isnot visible to a MySQL server.

The NDB API handles column names in case-sensitive fashion. For example, if you create a column named“myColumn”, you will not be able to access it later using“Mycolumn” for the name. You can reduce the possibility for error, by naming all columns consistently using only uppercase or only lowercase.

Signature

You can create either a new instance of theColumn class, or by copying an existingColumn object. Both of these are shown here:

• Constructor for a newColumn:

  Column    (      const char*name = ""    )

• Copy constructor:

  Column    (      const Column&column    )

Parameters

When creating a new instance ofColumn, the constructor takes a single argument, which is the name of the new column to be created. The copy constructor also takes one parameter—in this case, a reference to theColumn instance to be copied.

Return value

AColumn object.

Destructor

TheColumn class destructor takes no arguments and returns nothing (void).

Description

This method is used to compare oneColumn with another to determine whether the twoColumn objects are the same.

Signature

bool equal    (      const Column&column    ) const

Parameters

equal() takes a single parameter, a reference to an instance ofColumn.

Return value

true if the columns being compared are equal, otherwisefalse.

Description

This method gets the column's array type.

Signature

ArrayType getArrayType    (      void    ) const

Parameters

None.

Return value

AnArrayType; seeColumn::ArrayType for possible values.

Description

This method shows whether the column is an auto-increment column.

Signature

bool getAutoIncrement    (      void    ) const

Parameters

None.

Return value

TRUE if the column is an auto-increment column,FALSE if it is not.

Description

This gets the character set used by a text column.

This method is applicable only to columns whoseType value isChar,Varchar, orText.

The NDB API handles column names in case-sensitive fashion;“myColumn” and“Mycolumn” are not considered to refer to the same column. It is recommended that you minimize the possibility of errors from using the wrong lettercase for column names by naming all columns consistently using only uppercase or only lowercase.

Signature

CHARSET_INFO* getCharset    (      void    ) const

Parameters

None.

Return value

A pointer to aCHARSET_INFO structure specifying both character set and collation. This is the same as a MySQLMY_CHARSET_INFO data structure; for more information, seemysql_get_character_set_info(),in the MySQL Manual.

Description

This method gets the sequence number of a column within its containing table or index. If the column is part of an index (such as when returned bygetColumn()), it is mapped to its position within that index, and not within the table containing the index.

Signature

int getColumnNo    (      void    ) const

Parameters

None.

Return value

The column number as an integer.

Description

Gets a column's default value data.

To determine whether a table has any columns with default values, useTable::hasDefaultValues().

Signature

const void* getDefaultValue    (      unsigned int*len = 0    ) const

Parameters

len holds either the length of the default value data, or 0 in the event that the column is nullable or has no default value.

Return value

The default value data.

Description

This method retrieves the inline size of a blob column—that is, the number of initial bytes to store in the table's blob attribute. This part is normally in main memory and can be indexed.

This method is applicable only to blob columns.

Beginning with NDB 8.0.29, you can also obtain this information in themysql client, by querying thendbinfo.blobs table.

Signature

int getInlineSize    (      void    ) const

Parameters

None.

Return value

The blob column's inline size, as an integer.

Description

This method gets the length of a column. This is either the array length for the column or—for a variable length array—the maximum length.

Signature

int getLength    (      void    ) const

Parameters

None.

Return value

The (maximum) array length of the column, as an integer.

Description

This method returns the name of the column for which it is called.

The NDB API handles column names in case-sensitive fashion. For example, if you retrieve the name“myColumn” for a given column, attempting to access this column using“Mycolumn” for the name fails with an error such asColumn is NULL orTable definition has undefined column. You can reduce the possibility for error, by naming all columns consistently using only uppercase or only lowercase.

Signature

const char* getName    (      void    ) const

Parameters

None.

Return value

The name of the column.

Description

This method is used to determine whether the column can be set toNULL.

Signature

bool getNullable    (      void    ) const

Parameters

None.

Return value

A Boolean value:true if the column can be set toNULL, otherwisefalse.

Description

This method is used to check whether the column is part of the table's partitioning key.

Apartitioning key is a set of attributes used to distribute the tuples onto the data nodes. This key a hashing function specific to theNDB storage engine.

An example where this would be useful is an inventory tracking application involving multiple warehouses and regions, where it might be good to use the warehouse ID and district id as the partition key. This would place all data for a specific district and warehouse in the same storage node. Locally to each fragment the full primary key will still be used with the hashing algorithm in such a case.

For more information about partitioning, partitioning schemes, and partitioning keys in MySQL, seePartitioning, in the MySQL Manual.

The only type of user-defined partitioning that is supported for use with theNDB storage engine is key partitioning, including linear key partitioning.

Signature

bool getPartitionKey    (      void    ) const

Parameters

None.

Return value

true if the column is part of the partitioning key for the table, otherwisefalse.

Description

This method is used to get the blob part size of a BLOB column—that is, the number of bytes that are stored in each tuple of the blob table.

This method is applicable to BLOB columns only.

In NDB 8.0.29 and later, you can also obtain this information in themysql client or other MySQL client, by querying thendbinfo.blobs table.

Signature

int getPartSize    (      void    ) const

Parameters

None.

Return value

The column's part size, as an integer. In the case of aTinyblob column, this value is0 (that is, only inline bytes are stored).

Description

This method gets the precision of a column.

This method is applicable to decimal columns only.

Signature

int getPrecision    (      void    ) const

Parameters

None.

Return value

The column's precision, as an integer. The precision is defined as the number of significant digits; for more information, see the discussion of theDECIMAL data type inNumeric Data Types, in the MySQL Manual.

Description

This method is used to determine whether the column is part of the table's primary key.

Signature

bool getPrimaryKey    (      void    ) const

Parameters

None.

Return value

A Boolean value:true if the column is part of the primary key of the table to which this column belongs, otherwisefalse.

Description

This method gets the scale used for a decimal column value.

This method is applicable to decimal columns only.

Signature

int getScale    (      void    ) const

Parameters

None.

Return value

The decimal column's scale, as an integer. The scale of a decimal column represents the number of digits that can be stored following the decimal point. It is possible for this value to be0. For more information, see the discussion of theDECIMAL data type inNumeric Data Types, in the MySQL Manual.

Description

This function is used to obtain the size of a column.

Signature

int getSize    (      void    ) const

Parameters

None.

Return value

The column's size in bytes (an integer value).

Description

Gets the space required for a given column by anNdbRecord, depending on the column's type, as follows:

• For a BLOB column, this value is the same assizeof(NdbRecord*), which is 4 or 8 bytes (the size of a pointer; platform-dependent).

• For columns of all other types, it is the same as the value returned bygetSize().

This method was added in NDB NDB 7.4.7.

Signature

int getSizeInBytesForRecord    (      void    ) const

Parameters

None.

Return value

An integer (see Description).

Description

This method obtains a column's storage type.

Signature

StorageType getStorageType    (      void    ) const

Parameters

None.

Return value

AStorageType value; for more information about this type, seeColumn::StorageType.

Description

This method gets the stripe size of a blob column—that is, the number of consecutive parts to store in each node group.

Signature

int getStripeSize    (      void    ) const

Parameters

None.

Return value

The column's stripe size, as an integer.

Description

This method gets the column's data type.

Signature

Type getType    (      void    ) const

Parameters

None.

Return value

TheType (data type) of the column. For a list of possible values, seeColumn::Type.

Description

Sets the array type for the column.

Signature

void setArrayType    (      ArrayTypetype    )

Parameters

AColumn::ArrayType value. SeeColumn::ArrayType, for more information.

Return value

None.

Description

Make the column auto-incrementing (or not).

Signature

void setAutoIncrement    (      boolflag    )

Parameters

A boolean value:TRUE to make the column auto-incrementing;FALSE to remove this property of the column.

Return value

None.

Description

Set the initial value for an auto-incrementing column.

Signature

void setAutoIncrementInitialValue    (      Uint64value    )

Parameters

The initial value for the column (a 64-bit integer).

Return value

None.

Description

This method can be used to set the character set and collation of aChar,Varchar, orText column.

This method is applicable toChar,Varchar, andText columns only.

Changes made to columns using this method are not visible to MySQL.

Signature

void setCharset    (      CHARSET_INFO*cs    )

Parameters

This method takes one parameter.cs is a pointer to aCHARSET_INFO structure. For additional information, seeColumn::getCharset().

Return value

None.

Description

This method sets a column value to its default, if it has one; otherwise it sets the column toNULL.

To determine whether a table has any columns with default values, useTable::hasDefaultValues().

Signature

int setDefaultValue    (      const void*buf,      unsigned intlen    )

Parameters

This method takes 2 arguments: a value pointerbuf; and the lengthlen of the data, as the number of significant bytes. For fixed size types, this is the type size. For variable length types, the leading 1 or 2 bytes pointed to bybuffer also contain size information as normal for the type.

Return value

0 on success, 1 on failure..

Description

This method gets the inline size of a blob column—that is, the number of initial bytes to store in the table's blob attribute. This part is normally kept in main memory, and can be indexed and interpreted.

This method is applicable to blob columns only.

Changes made to columns using this method are not visible to MySQL. Beginning with NDB 8.0.30, you can change the inline size of a blob column in themysql client by settingBLOB_INLINE_SIZE in a column comment as part ofCREATE TABLE orALTER TABLE. SeeNDB_COLUMN Options, for more information.

Signature

void setInlineSize    (      intsize    )

Parameters

The integersize is the new inline size for the blob column.

Return value

None.

Description

This method sets the length of a column. For a variable-length array, this is the maximum length; otherwise it is the array length.

Changes made to columns using this method are not visible to MySQL.

Signature

void setLength    (      intlength    )

Parameters

This method takes a single argument—the integer valuelength is the new length for the column.

Return value

None.

Description

This method is used to set the name of a column.

setName() is the onlyColumn method whose result is visible from a MySQL Server. MySQL cannot see any other changes made to existing columns using the NDB API.

Signature

void setName    (      const char*name    )

Parameters

This method takes a single argument—the new name for the column.

Return value

This methodNone.

Description

This method toggles the nullability of a column.

Changes made to columns using this method are not visible to MySQL.

Signature

void setNullable    (      boolnullable    )

Parameters

A Boolean value. Usingtrue makes it possible to insertNULLs into the column; ifnullable isfalse, then this method performs the equivalent of changing the column toNOT NULL in MySQL.

Return value

None.

Description

This method makes it possible to add a column to the partitioning key of the table to which it belongs, or to remove the column from the table's partitioning key.

Changes made to columns using this method are not visible to MySQL.

For additional information, seeColumn::getPartitionKey().

Signature

void setPartitionKey    (      boolenable    )

Parameters

The single parameterenable is a Boolean value. Passingtrue to this method makes the column part of the table's partitioning key; ifenable isfalse, then the column is removed from the partitioning key.

Return value

None.

Description

This method sets the blob part size of a blob column—that is, the number of bytes to store in each tuple of the blob table.

This method is applicable to blob columns only.

Changes made to columns using this method are not visible to MySQL. You can increase the blob part size of a blob column to the maximum supported byNDB (13948) inmysql or another MySQL client by setting theMAX_BLOB_PART_SIZE option in a column comment as part of aCREATE TABLE orALTER TABLE statement. SeeNDB_COLUMN Options.

Signature

void setPartSize    (      intsize    )

Parameters

The integersize is the number of bytes to store in the blob table. Using zero for this value means only inline bytes can be stored, in effect making the column's typeTINYBLOB.

Return value

None.

Description

This method can be used to set the precision of a decimal column.

This method is applicable to decimal columns only.

Changes made to columns using this method are not visible to MySQL.

Signature

void setPrecision    (      intprecision    )

Parameters

This method takes a single parameter—precision is an integer, the value of the column's new precision. For additional information about decimal precision and scale, seeColumn::getPrecision(), andColumn::getScale().

Return value

None.

Description

This method is used to make a column part of the table's primary key, or to remove it from the primary key.

Changes made to columns using this method are not visible to MySQL.

Signature

void setPrimaryKey    (      boolprimary    )

Parameters

This method takes a single Boolean value. If it istrue, then the column becomes part of the table's primary key; iffalse, then the column is removed from the primary key.

Return value

None.

Description

This method can be used to set the scale of a decimal column.

This method is applicable to decimal columns only.

Changes made to columns using this method are not visible to MySQL.

Signature

void setScale    (      intscale    )

Parameters

This method takes a single parameter—the integerscale is the new scale for the decimal column. For additional information about decimal precision and scale, seeColumn::getPrecision(), andColumn::getScale().

Return value

None.

Description

This method sets the stripe size of a blob column—that is, the number of consecutive parts to store in each node group.

This method is applicable to blob columns only.

Changes made to columns using this method are not visible to MySQL.

Signature

void setStripeSize    (      intsize    )

Parameters

This method takes a single argument. The integersize is the new stripe size for the column.

Return value

None.

Description

Sets the storage type for the column.

Signature

void setStorageType    (      StorageTypetype    )

Parameters

AColumn::StorageType value. SeeColumn::StorageType, for more information.

Return value

None.

Description

This method sets theType (data type) of a column.

setType() resets all column attributes to their (type dependent) default values; it should be the first method that you call when changing the attributes of a given column.

Changes made to columns using this method are not visible to MySQL.

Signature

void setType    (      Typetype    )

Parameters

This method takes a single parameter—the newColumn::Type for the column. The default isUnsigned. For a listing of all permitted values, seeColumn::Type.

Return value

None.

Description

The storage type used for a given column can be either in memory or on disk. Columns stored on disk mean that less RAM is required overall but such columns cannot be indexed, and are potentially much slower to access. The default isStorageTypeMemory.

Enumeration values

Possible values are shown, along with descriptions, in the following table:

Table 2.9 Column object StorageType data type values and descriptions

Name	Description
StorageTypeMemory	Store the column in memory
StorageTypeDisk	Store the column on disk

Description

Data types forColumn objects are analogous to the data types used by MySQL. The typesTinyint,Tinyintunsigned,Smallint,Smallunsigned,Mediumint,Mediumunsigned,Int,Unsigned,Bigint,Bigunsigned,Float, andDouble (that is, typesTinyint throughDouble in the order listed in the Enumeration Values table) can be used in arrays.

Do not confuseColumn::Type withObject::Type.

Enumeration values

Possible values are shown, along with descriptions, in the following table:

Table 2.10 Column object Type data type values and descriptions

Name	Description
Undefined	Undefined
Tinyint	1-byte signed integer
Tinyunsigned	1-byte unsigned integer
Smallint	2-byte signed integer
Smallunsigned	2-byte unsigned integer
Mediumint	3-byte signed integer
Mediumunsigned	3-byte unsigned integer
Int	4-byte signed integer
Unsigned	4-byte unsigned integer
Bigint	8-byte signed integer
Bigunsigned	8-byte signed integer
Float	4-byte float
Double	8-byte float
Olddecimal	Signed decimal as used prior to MySQL 5.0 (OBSOLETE)
Olddecimalunsigned	Unsigned decimal as used prior to MySQL 5.0 (OBSOLETE)
Decimal	Signed decimal as used by MySQL 5.0 and later
Decimalunsigned	Unsigned decimal as used by MySQL 5.0 and later
Char	A fixed-length array of 1-byte characters; maximum length is 255 characters
Varchar	A variable-length array of 1-byte characters; maximum length is 255 characters
Binary	A fixed-length array of 1-byte binary characters; maximum length is 255 characters
Varbinary	A variable-length array of 1-byte binary characters; maximum length is 255 characters
Datetime	An 8-byte date and time value, with a precision of 1 second (DEPRECATED)
Datetime2	An 8-byte date and time value, with fractional seconds.
Date	A 4-byte date value, with a precision of 1 day
Blob	A binary large object; seeSection 2.3.13, “The NdbBlob Class”
Text	A text blob
Bit	A bit value; the length specifies the number of bits
Longvarchar	A 2-byteVarchar
Longvarbinary	A 2-byteVarbinary
Time	Time without date (DEPRECATED)
Time2	Time without date, with fractional seconds.
Year	1-byte year value in the range 1901-2155 (same as MySQL)
Timestamp	Unix time (DEPRECATED)
Timestamp2	Unix time, with fractional seconds.