Class ObjectSchema.ColumnStoreDictionary

Namespace

LinqToDB.Tools.DataProvider.SqlServer.Schemas

Assembly

linq2db.Tools.dll

sys.column_store_dictionaries (Transact-SQL)

Applies to: √ SQL Server (all supported versions)

Contains a row for each dictionary used in xVelocity memory optimized columnstore indexes. Dictionaries are used to encode some, but not all data types, therefore not all columns in a columnstore index have dictionaries. A dictionary can exist as a primary dictionary (for all segments) and possibly for other secondary dictionaries used for a subset of the column's segments.

See sys.column_store_dictionaries.

[Table(Schema = "sys", Name = "column_store_dictionaries", IsView = true)]
public class ObjectSchema.ColumnStoreDictionary

Inheritance

object

ObjectSchema.ColumnStoreDictionary

Extension Methods

Map.DeepCopy<T>(T)

Properties

ColumnID

ID of the columnstore column starting with 1. The first column has ID = 1, the second column has ID = 2, etc.

[Column("column_id")]
[Nullable]
public int? ColumnID { get; set; }

Property Value

int?

DictionaryID

There can be two kinds of dictionaries, global and local, associated with a column segment. A dictionary_id of 0 represents the global dictionary that is shared across all column segments (one for each row group) for that column.

[Column("dictionary_id")]
[Nullable]
public int? DictionaryID { get; set; }

Property Value

int?

EntryCount

Number of entries in the dictionary.

[Column("entry_count")]
[Nullable]
public long? EntryCount { get; set; }

Property Value

long?

HoBTID

ID of the heap or B-tree index (HoBT) for the table that has this columnstore index.

[Column("hobt_id")]
[Nullable]
public long? HoBTID { get; set; }

Property Value

long?

LastID

The last data ID in the dictionary.

[Column("last_id")]
[Nullable]
public int? LastID { get; set; }

Property Value

int?

OnDiskSize

Size of dictionary in bytes.

[Column("on_disk_size")]
[Nullable]
public long? OnDiskSize { get; set; }

Property Value

long?

PartitionID

Indicates the partition ID. Is unique within a database.

[Column("partition_id")]
[Nullable]
public long? PartitionID { get; set; }

Property Value

long?

TypeColumn

Dictionary type:

1 - Hash dictionary containing int values

2 - Not used

3 - Hash dictionary containing string values

4 - Hash dictionary containing float values

For more information about dictionaries, see Columnstore Indexes Guide.

[Column("type")]
[Nullable]
public int? TypeColumn { get; set; }

Property Value

int?

Version

Version of the dictionary format.

[Column("version")]
[Nullable]
public int? Version { get; set; }

Property Value

int?