`CREATE TABLE`¶

Define a new table.

Table of Contents

Synopsis ¶

CREATE TABLE [ IF NOT EXISTS ] table_ident ( [
    {
        base_column_definition
      | generated_column_definition
      | table_constraint
    }
    [, ... ] ]
)
[ PARTITIONED BY (column_name [, ...] ) ]
[ CLUSTERED [ BY (routing_column) ] INTO num_shards SHARDS ]
[ WITH ( table_parameter [= value] [, ... ] ) ]

where base_column_definition:

column_name data_type [ column_constraint [ ... ] ]  [ storage_options ]

where generated_column_definition is:

column_name [ data_type ] [ GENERATED ALWAYS ]
AS [ ( ] generation_expression [ ) ]
[ column_constraint [ ... ] ]

where column_constraint is:

{ PRIMARY KEY |
  NOT NULL |
  INDEX { OFF | USING { PLAIN |
                        FULLTEXT [ WITH ( analyzer = analyzer_name ) ]  }
}

where storage_options is:

STORAGE WITH ( option = value_expression [, ... ] )

and table_constraint is:

{ PRIMARY KEY ( column_name [, ... ] ) |
  INDEX index_name USING FULLTEXT ( column_name [, ... ] )
       [ WITH ( analyzer = analyzer_name ) ]
}

Description ¶

CREATE TABLE will create a new, initially empty table.

If the table_ident does not contain a schema, the table is created in the doc schema. Otherwise it is created in the given schema, which is implicitly created, if it didn’t exist yet.

A table consists of one or more base columns and any number of generated columns and/or table_constraints.

The optional constraint clauses specify constraints (tests) that new or updated rows must satisfy for an insert or update operation to succeed. A constraint is an SQL object that helps define the set of valid values in the table in various ways.

There are two ways to define constraints: table constraints and column constraints. A column constraint is defined as part of a column definition. A table constraint definition is not tied to a particular column, and it can encompass more than one column. Every column constraint can also be written as a table constraint; a column constraint is only a notational convenience for use when the constraint only affects one column.

Table Elements ¶

Base Columns ¶

A base column is a persistent column in the table metadata. In relational terms it is an attribute of the tuple of the table-relation. It has a name, a type and optional constraints.

Base columns are readable and writable (if the table itself is writable). Values for base columns are given in DML statements explicitly or omitted, in which case their value is null.

Generated Columns ¶

A generated column is a persistent column that is computed as needed from the generation_expression for every INSERT and UPDATE operation.

The GENERATED ALWAYS part of the syntax is optional.

Note

A generated column is not a virtual column. The computed value is stored in the table like a base column is. The automatic computation of the value is what makes it different.

Table Constraints ¶

Table constraints are constraints that are applied to more than one column or to the table as a whole.

For further details see Constraints.

Column Constraints ¶

Column constraints are constraints that are applied on each column of the table separately.

For further details see Column Constraints.

Storage options ¶

Storage options can be applied on each column of the table separately.

For further details and available options see Storage.

Parameters ¶

table_ident: The name (optionally schema-qualified) of the table to be created.
column_name: The name of a column to be created in the new table.
data_type: The data type of the column. This can include array and object specifiers. For more information on the data types supported by CrateDB see Data Types.
generation_expression: An expression (usually a function call) that is applied in the context of the current row. As such it can reference other base columns of the table. Referencing other generated columns (including itself) is not supported. The generation expression is evaluated each time a row is inserted or the referenced base columns are updated.

`IF NOT EXISTS`¶

If the optional IF NOT EXISTS clause is used this statement won’t do anything if the table exists already.

`CLUSTERED`¶

The optional CLUSTERED clause specifies how a table should be distributed accross a cluster.

num_shards

Specifies the number of shards a table is stored in. Must be greater than 0. If not provided the number of shards is calculated based on the number of currently active data nodes with the following formula:

num_shards = max(4, num_data_nodes * 2)

Note

The minimum value of num_shards is set to 4. This means if the calculation of num_shards does not exceeds its minimum it applies the minimum value to each table or partition as default.

routing_column

Allows to explicitly specify a column or field on which basis rows are sharded. All rows having the same value in routing_column are stored in the same shard. The default is the primary key if specified, otherwise the internal _id column.

`PARTITIONED BY`¶

The PARTITIONED clause splits the created table into separate partitions for every distinct combination of values in the listed columns.

[ PARTITIONED BY ( column_name [ , ... ] ) ]

column_name: A column from the table definition this table gets partitioned by.

Several restrictions apply to columns that can be used here:

columns may not be part of CLUSTERED.
columns must have a primitive type.
columns may not be inside an object array.
columns may not be indexed with a Fulltext Index With Analyzer.
if the table has a Tables Constraints the columns in PARTITIONED clause have to be part of it

Note

Columns referenced in the PARTITIONED clause cannot be altered by an UPDATE statement.

`WITH`¶

The optional WITH clause can specify parameters for tables.

[ WITH ( table_parameter [= value] [, ... ] ) ]

table_parameter: Specifies an optional parameter for the table.

Note

Some parameters are nested, and therefore need to be wrapped in double quotes in order to be set: WITH ("allocation.max_retries" = 5). Nested parameters are those that contain a . between parameter names, e.g. write.wait_for_active_shards.

Available parameters are:

`number_of_replicas`¶

Specifies the number or range of replicas each shard of a table should have for normal operation, the default is to have 0-1 replica.

The number of replicas is defined like this:

min_replicas [ - [ max_replicas ] ]

min_replicas

The minimum number of replicas required.

max_replicas

The maximum number of replicas.

The actual maximum number of replicas is max(num_replicas, N-1), where N is the number of data nodes in the cluster. If max_replicas is the string all then it will always be N.

For further details and examples see Replication.

`number_of_routing_shards`¶

This number specifies the hashing space that is used internally to distribute documents across shards.

This is an optional setting that enables users to later on increase the number of shards using ALTER TABLE.

`refresh_interval`¶

Specifies the refresh interval of a shard in milliseconds. The default is set to 1000 milliseconds.

value: The refresh interval in milliseconds. A value of smaller or equal than 0 turns off the automatic refresh. A value of greater than 0 schedules a periodic refresh of the table.

Note

A refresh_interval of 0 does not guarantee that new writes are NOT visible to subsequent reads. Only the periodic refresh is disabled. There are other internal factors that might trigger a refresh.

For further details see Refresh or REFRESH.

`write.wait_for_active_shards`¶

Specifies the number of shard copies that need to be active for the write operation to proceed. If less shards are active the operation will wait for 30s for them to become active or timeout.

The number of shard copies is defined like this:

number_of_shard_copies = (1 + number_of_replicas)

value: The number of active shard copies to wait for or all. The default value is set to all which will cause write operations to wait for the primary and all replica shards to be active.

`blocks.read_only`¶

Allows to have a read only table.

value: Table is read only if value set to true. Allows writes and table settings changes if set to false.

`blocks.read_only_allow_delete`¶

Allows to have a read only table that additionally can be deleted.

value: Table is read only and can be deleted if value set to true. Allows writes and table settings changes if set to false. When a disk on a node exceeds the cluster.routing.allocation.disk.watermark.flood_stage threshold, this block is applied (set to true) to all tables on that affected node. Once you’ve freed disk space again and the threshold is undershot, you need to set the blocks.read_only_allow_delete table setting to false.

`blocks.read`¶

disable/enable all the read operations

value: Set to true to disable all read operations for a table, otherwise set false.

`blocks.write`¶

disable/enable all the write operations

value: Set to true to disable all write operations and table settings modifications, otherwise set false.

`blocks.metadata`¶

disable/enable the table settings modifications.

values: Disables the table settings modifications if set to true, if set to false — table settings modifications are enabled.

`mapping.total_fields.limit`¶

Sets the maximum number of columns that is allowed for a table. Default is 1000.

value: Maximum amount of fields in the Lucene index mapping. This includes both the user facing mapping (columns) and internal fields.

`translog.flush_threshold_size`¶

Sets size of transaction log prior to flushing.

value: Size (bytes) of translog.

`translog.disable_flush`¶

enable/disable flushing.

value: Set true to disable flushing, otherwise set to false.

Caution

It is recommended to use disable_flush only for short periods of time.

`translog.interval`¶

Sets frequency of flush necessity check.

value: Frequency in milliseconds.

`translog.sync_interval`¶

How often the translog is fsynced to disk. Defaults to 5s. When setting this interval, please keep in mind that changes logged during this interval and not synced to disk may get lost in case of a failure. This setting only takes effect if translog.durability is set to ASYNC.

value: Interval in milliseconds.

`translog.durability`¶

If set to ASYNC the translog gets flushed to disk in the background every translog.sync_interval. If set to REQUEST the flush happens after every operation.

value: REQUEST (default), ASYNC

`routing.allocation.total_shards_per_node`¶

Controls the total number of shards (replicas and primaries) allowed to be allocated on a single node. Defaults to unbounded (-1).

value: Number of shards per node.

`routing.allocation.enable`¶

Controls shard allocation for a specific table. Can be set to:

all: Allows shard allocation for all shards. (Default)
primaries: Allows shard allocation only for primary shards.
new_primaries: Allows shard allocation only for primary shards for new tables.
none: No shard allocation allowed.

`routing.allocation.max_retries`¶

Defines the number of attempts to allocate a shard before giving up and leaving the shard unallocated.

value: Number of retries to allocate a shard. Defaults to 5.

`routing.allocation.include.{attribute}`¶

Assign the table to a node whose {attribute} has at least one of the comma-separated values. See Shard Allocation Filtering for details.

`routing.allocation.require.{attribute}`¶

Assign the table to a node whose {attribute} has all of the comma-separated values. See Shard Allocation Filtering for details.

`routing.allocation.exclude.{attribute}`¶

Assign the table to a node whose {attribute} has none of the comma-separated values. See Shard Allocation Filtering for details.

`warming.enable`¶

disable/enable table warming.

Table warming allows to run registered queries to warm up the table before it is available.

Enabled by default.

value: true` to enable warming up, otherwise false

`unassigned.node_left.delayed_timeout`¶

Delay the allocation of replica shards which have become unassigned because a node has left. It defaults to 1m to give a node time to restart completely (which can take some time when the node has lots of shards). Setting the timeout to 0 will start allocation immediately. This setting can be changed on runtime in order to increase/decrease the delayed allocation if needed.

`column_policy`¶

Specifies the column policy of the table. The default column policy is dynamic.

The column policy is defined like this:

WITH ( column_policy = {'dynamic' | 'strict'} )

strict: Rejecting any column on insert, update or copy from which is not defined in the schema
dynamic: New columns can be added using insert, update or copy from. New columns added to dynamic tables are, once added, usable as usual columns. One can retrieve them, sort by them and use them in where clauses.

For futher details and examples see Column Policy or Configuration.

`max_ngram_diff`¶

Specifies the maximum difference between max_ngram and min_ngram when using the NGramTokenizer or the NGramTokenFilter. The default is 1.

`max_shingle_diff`¶

Specifies the maximum difference between min_shingle_size and max_shingle_size when using the ShingleTokenFilter. The default is 3.

CREATE TABLE¶

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`CREATE TABLE`¶