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DDM UMN 1st v Reviewed-by: Wagner, Fabian <fabian.wagner@t-systems.com> Co-authored-by: proposalbot <proposalbot@otc-service.com> Co-committed-by: proposalbot <proposalbot@otc-service.com>
114 lines
3.3 KiB
ReStructuredText
114 lines
3.3 KiB
ReStructuredText
:original_name: ddm_12_0010.html
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.. _ddm_12_0010:
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Overview
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========
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Global sequences are mainly database-based global sequences.
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.. note::
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- The start auto-increment SN can be modified.
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- Global sequence provides sequence numbers that are globally unique but may not increase continuously.
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.. table:: **Table 1** Table types supported by global sequence
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========== ========= ========= =============
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Table Type Sharded Broadcast Unsharded
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========== ========= ========= =============
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DB-based Supported Supported Not supported
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========== ========= ========= =============
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Creating an Auto-Increment Sequence
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-----------------------------------
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#. Log in to the required DDM instance using a client.
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#. Open the required schema.
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#. Run the following command to create an auto-increment sequence:
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**create sequence** <seq_name>;
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.. note::
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- *<seq_name>* indicates the sequence name.
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- The auto-increment key should be a BIGINT value. To avoid duplicate values, do not use TINYINT, SMALLINT, MEDIUMINT, INTEGER, or INT as the auto-increment key.
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- Run **show sequences** to view the usage of the auto-increment sequence. If the usage reaches 100%, do not insert data anymore.
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Dropping an Auto-Increment Sequence
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-----------------------------------
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#. Log in to the required DDM instance using a client.
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#. Open the required schema.
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#. Run **show sequences** to view all global sequences.
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#. Run the following command to drop an auto-increment sequence:
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**drop sequence** <seq_name> ;
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**drop sequence** *DB.*\ <seq_name>;
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.. note::
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- The sequence name is case-insensitive.
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- If an auto-increment sequence is inherent to a table, the sequence cannot be deleted.
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Modifying the Start Value of an Auto-Increment Sequence
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-------------------------------------------------------
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#. Log in to the required DDM instance using a client.
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#. Open the required schema.
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#. Run **show sequences** to view all global sequences.
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#. Run the command to change the start value:
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**alter sequence** <seq_name> **START WITH** <start_value>\ *;*
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.. note::
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- *<seq_name>* indicates the sequence name.
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- *<start_value>* indicates the start value of the target sequence.
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Querying an Auto-Increment Sequence
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-----------------------------------
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#. Log in to the required DDM instance using a client.
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#. Open the required schema.
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#. Run **show sequences** to view all global sequences.
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**show sequences**;
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|image1|
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Modifying the Auto-Increment Cache Value
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----------------------------------------
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.. important::
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This feature is only available in kernel 3.0.3 and later versions.
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#. Log in to the required DDM instance using a client.
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#. Open the required schema.
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#. Run command **alter sequence test cache 5000** to modify the global sequence cache value of table **test**.
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#. Run command **show sequences** to view the cache value (**INCREMENT** value) of table **test**.
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Updating Auto-Increment Sequences of All Tables
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-----------------------------------------------
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.. important::
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This feature is available only in kernel 3.0.4.1 or later.
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#. Log in to the required DDM instance using a client.
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#. Run command **fresh all sequence start value** to change sequences of all schemas.
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.. |image1| image:: /_static/images/en-us_image_0000001685307306.jpg
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