The following limitations in previous versions have been resolved:

It was possible in an XDCR environment for the replay of binary logs from one cluster to interfere with the local transactions on the other cluster, resulting in high latency. The application of binary logs has been tuned to reduce the impact on the local client workload.

There was a condition where if, after using database replication (DR) and one of the clusters stops and recovers, the cluster could fail with a ConcurrentModificationException exception. This condition was caused by the partitions used for DR changing while the cluster was down and the partition mapping from one cluster to the other being out of sync. This issue has been resolved.

In rare cases, a master database could report a null pointer exception and stall replication if the consumer cluster encountered a change in its topology (that is, a node failed or rejoined). A common symptom before the master cluster stalled was that it reported a series of informational messages that DR was "discarding ctrl message". This issue has been resolved.

When configuring database replication (DR), you can now specify multiple servers, separated by commas, in the source attribute of the <connection> tag in the deployment file. This way, DR can start even if one of the listed servers on the master cluster is currently down. For example:

<dr id="2">
  <connection source="server1,server2" />
</dr>

There is a new flag, --wait, available for the voltadmin pause command. With the --wait flag, the command waits until all pending transactions are processed and all database replication (DR) and export queues are flushed before returning control to the shell prompt. This can be useful when scripting the shutdown of the database, for example. Without the --wait flag, the pause command returns immediately, without waiting for the database to actually quiesce.

Normally, VoltDB refuses to start on Linux systems if Transparent Huge Pages (THP) are enabled, because THP are known to cause issues for memory-intensive applications like VoltDB. However, if you want to run simple tests using VoltDB without reconfiguring your Linux server, you can use the --ignore=thp flag when starting the server. For example:

$ voltdb create --ignore=thp

This flag is not supported and should never be used on production systems because of the problems THP can cause.

A new method in the VoltProcedure class returns the current cluster ID. The VoltProcedure.getClusterId() method returns the cluster ID specified when configuring database replication in the deployment file. The cluster ID is the unique ID listed in the id attribute of the <dr> tag. For example, the following deployment file sets the cluster ID to the value 2:

<dr id="2">

You can combine the return value of this new method with the .getUniqueId() method to generate an ID that is unique across multiple clusters, which is especially useful when using cross datacenter replication (XDCR).

The resilience of database replication (DR) to continue in the face of network fluctuations has been improved. DR is less likely to break as a result of a network glitch than in previous releases.

There is a new attribute when configuring import in the deployment file. The format attribute lets you choose between comma-separated values (csv) and tab-separated (tsv) format for the imported data. For example, the following configuration specifies tab-delimited input:

<import>
  <configuration type="kafka" format="tsv" enabled="true">
      . . .

The default for the format attribute is csv.

VoltDB now supports the use of custom importers through the use of the type="custom" and module="{bundle}" attributes. For example:

<import>
  <configuration module=“mybundle.jar” type=“custom” enabled=“true">
    <property name=“myprop1”>val1</property>
    <property name=“myprop2”>val2</property>
  </configuration>
</import>

Contact support@voltdb.com for further Information on how to write custom importers.

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

This release adds three new SQL functions:DATEADD(). PI(), and REGEXP_POSITION(). See the Using VoltDB appendix of SQL functions for details.

With the current release, VoltDB drops support for OS X release 10.7.

In addition to the features described above, the following limitations in previous versions have been resolved:

VoltDB is proud to announce the availability of Cross Datacenter Replication (XDCR), two-way active replication across two database clusters. XDCR provides the ability to maintain separate but synchronized writable databases in two separate locations. For more information, read the updated chapter on Database Replication in the Using VoltDB manual and contact your VoltDB sales representative. (XDCR is a separately licensed product feature.)

The information available from the @Statistics system procedure have been extended and improved. First, a new selector, IMPORTER, has been added which provides statistics about the performance of the import function.

Second, the selector DR, has been renamed DRPRODUCER to be more descriptive and complement the existing DRCONSUMER selector. Note that despite the name change, the old name for the selector, DR, will continue to be recognized for backwards compatibility.

Finally, the value of the status column SYNC​SNAPSHOT​STATE returned by the DRPRODUCER selector has been changed. If no synchronization snapshot is occurring, the status column now returns the value "NONE".

Floating point datatypes approximate decimal values with a high but not perfect level of precision. As a result, arithmetic with floating point values, especially aggregation of multiple values is capable of generating slightly different values if aggregated in different orders. As a result, it is possible for use of aggregate functions on floating point column values to be non-deterministic.

VoltDB now generates non-determinism warnings if read/write stored procedures include queries that use the aggregate functions AVG() or SUM() on floating point columns. For precise decimal arithmetic, especially involving aggregate functions, use of the DECIMAL datatype is recommended.

Short VARCHAR and VARBINARY strings are stored inline in the database record. Longer strings are managed in a separate pool using pointers. With this release the pointers used to manage longer string values have been optimized, reducing their size from 24 bytes per string to just 8 bytes. This reduces the overall memory required for databases with long string columns. Also, for performance reasons, the memory for string pointers is managed as a pool rather than being returned to the operating system with each DELETE operation. Consequently, optimizing the pointer size reduces the overall size of the pool retained by VoltDB when large numbers of string values are deleted (for example, after a TRUNCATE TABLE statement).

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

An issue exists in the initial 5.7 release, where if database replication is enabled and an update operation includes a null column value, the database cluster receiving the DR transaction log could crash while attempting to apply the DR log. This issue has been resolved.

It is now possible to include VARBINARY columns in indexes, including the primary key for the table.

It is now possible to create a snapshot that contains only a subset of all of the tables in the database. This feature is useful for creating backups of selected tables or to reduce the size of snapshots for applications that contain large static tables and want to save only those tables that change frequently.

To create a snapshot with a subset of the database tables, you must use either the JSON-encoded arguments to the @SnapshotSave system procedure or the --tables and --skiptables flags to the voltadmin save shell command. In either case, you can specify either the tables to include (tables) or the tables to exclude (skiptables) from the snapshot as a comma-separated list. For example, both of the following commands create a snapshot containing the votes and contestants tables from the voter example application:

$ voltadmin save --tables=votes,contestants /tmp/ incpart

$ sqlcmd
1> exec @SnapshotSave '{uripath:"file:///tmp/", "nonce":"incpart",
2>     "tables":["votes","contestants"]}';

Whereas the following commands create a snapshot excluding just the votes table:

$ voltadmin save --skiptables=votes /tmp/ excpart

$ sqlcmd
1> exec @SnapshotSave '{uripath:"file:///tmp/", "nonce":"excpart",
2>     "skiptables":["votes"]}';

Previously, manually restoring a snapshot (with the voltadmin restore command or @SnapshotRestore system procedure) only restored the data, it was up to the user to reinstate the appropriate schema before performing the restore. Now, if there is no existing schema (that is, no tables are defined in the database), the restore operation will automatically restore the schema from the snapshot before restoring the data. This makes it possible to do a save and restore around a maintenance window (such as upgrading the VoltDB software) without having to manually reload the schema.

If tables do exist in the database, the old behavior of restoring just the data persists. This allows you to perform certain schema modifications that are not possible while the database is running (such as changing the partitioning column of a table with data in it) by saving a snapshot, restarting the database, loading the new schema, and restoring just the data.

The INITIATOR selector for the @Statistics system procedure returns information about stored procedure invocations. The INITIATOR statistics now include data from the stored procedure invocations associated with the import feature as well. In the return values for the INITIATOR selector, import activity is reported with the name of the importer in the CONNECTION_HOSTNAME column and the name of the import procedure in the PROCEDURE_NAME column.

The WHERE clause now supports the IS DISTINCT FROM and IS NOT DISTINCT FROM boolean operators. IS DISTINCT FROM and IS NOT DISTINCT FROM are similar to the equals ("=") and not equals ("<>") operators respectively, except when evaluating null operands. Equals and not equals return false if either operand is a null. IS DISTINCT FROM and IS NOT DISTINCT FROM treat nulls as valid values. See the description of the SELECT statement in the Using VoltDB manual for more information.

Previously, there was no way to explicitly close a VoltDB connection within the PHP client library. A close method has been added. See the examples folder in the PHP client library kit, available from the VoltDB web site, for more information.

Administrators can set a system-wide query timeout for read-only queries in the deployment file when the database first starts. Any read-only queries that exceed the system-wide timeout limit are canceled.

It is now possible for users to set a timeout for individual read-only queries as well. There is a new method in the Java client API, callProcedureWithTimeout, that can be used in place of callProcedure to specify a query timeout for the call. You specify the timeout as an integer number of milliseconds. Interactive users can use the --query-timeout flag when starting the sqlcmd command line utility to specify a query timeout for all read-only queries in that sqlcmd session.

When security is enabled, only users with ADMIN privileges are allowed to set a per-transaction timeout that is longer than the system-wide timeout. However, all users can set a shorter query timeout.

The web-based VoltDB Management Center (VMC) is enhanced at each release, adding new capabilities as features are added to the VoltDB product. For example, with this release the Admin tab shows the configuration for the DR overflow directory, which was missing previously.

We also try to make the management center as clear and usable as possible, so occasionally we rearrange features to maximize usability. For this release the default graphs and data tables shown on the Monitor tab have been changed. By default, only the Latency, TPS, Memory and CPU graphs are shown. You can customize this display by clicking on the "Show More/Fewer Charts" button and selecting the graphs that you want displayed. Your choices are saved and reused across sessions via browser cookies. We hope you find the new defaults useful and appreciate any feedback you may have regarding these changes. Feel free to comment in our forums. Thank you.

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

It is now possible to automatically pause the database when memory or disk space exceeds a defined limit. Using the <resourcemonitor>, <memorylimit>, and <disklimit> tags, you can specify either a fixed size (in gigabytes) or a percentage of the total resource as a limit for the process resident set size or total disk usage. For example:

<systemsettings>
  <resourcemonitor>
     <memorylimit size="10"/>
     <disklimit>
        <feature name="snapshots" size="75%"/>
     </disklimit>
  </resourcemonitor>
</systemsettings>

See the VoltDB Administrator's Guide chapter on monitoring for details.

Beta testing of the import feature in VoltDB has been completed. This feature is now supported for production use.

The built-in import feature now supports the ability to import multiple streams to different tables or stored procedures. By including multiple <configuration> sections in the <import> element of the deployment file, you can have different Kafka topics from a single set of brokers, or from different brokers, imported to separate tables. For example:

<import>
  <configuration type="kafka" enabled="true">
    <property name="brokers">kafkasvr:9092</property>
    <property name="topics">employees</property>
    <property name="procedure">EMPLOYEE.insert</property>
  </configuration>
  <configuration type="kafka" enabled="true">
    <property name="brokers">kafkasvr:9092</property>
    <property name="topics">managers</property>
    <property name="procedure">MANAGER.insert</property>
  </configuration>
</import>

Also note that the type="kafka" attribute is now supported as a production importer. See the import/export chapter of the Using VoltDB manual for details.

The Kakfa export connector has been improved to avoid issues when using synchronized export. The acks.retry.timeout property avoids the export connector hanging when the Kafka infrastructure becomes unresponsive. You can specify a timeout period in milliseconds, after which the packet is assumed lost and is resent to the Kafka broker. See the import/export chapter of the Using VoltDB manual for details.

The voltdb check command lets you verify that your Linux server configuration meets VoltDB requirements before starting the database. The command checks such things as system settings (swappiness, transparent huge pages, etc), software versions, and whether necessary services (such as NTP) are running or not.

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

In previous releases, under certain circumstances, starting VoltDB on Macintosh OS X could result in an allocation (malloc) error and segmentation fault. This problem has been fixed.

Transparent Huge Pages (THP) are a new feature in recent Linux releases (Ubuntu starting with 14.04 and RHEL 6.x) that can cause issues for memory-intensive application like VoltDB. Consequently, VoltDB will now check for THP and refuse to start if they are enabled. See the VoltDB Administrator's Guide for instructions on disabling THP.

VoltDB is adding a new feature that allows data to be imported automatically when the database starts, in much the same way the existing export feature lets you export data. For the initial beta release, a Kafka importer is provided. You can learn more in t. Note: this feature is a beta release and should not be used for production systems.

The Kafka export connector has been updated to support the latest Kafka release, version 0.8.2. This version of Kafka significantly changes how Kafka producers work and so the properties for configuring Kafka export have changed as well. For example, the producer.type property is no longer valid. Customers currently using Kafka export may need to change their deployment files when upgrading. Please read the section on Kafka Export in the Using VoltDB manual for details.

A new export connector is available that exports data to Elasticsearch. Elasticsearch is a full-text search service that makes it possible to search VoltDB data more flexibly and faster than using VoltDB alone. See the section on Elasticsearch export in the Using VoltDB manual for details.

K-safety increases the availability of a VoltDB database by duplicating partitions on different servers. By default, K-safety assumes all servers are distinct. However, in reality this is not always the case, for example in virtualized or hosted environments where multiple virtual servers could be running on the same hardware or on a rack sharing a power supply.

You can now provide hints to the cluster to improve the placement of duplicate partitions. The --placement-group flag to the voltdb create or recover commands lets you specify a group of names, separated by periods, that specify the location of the server process. For example:

$ voltdb create --placement-group=row5.rack3.server12 

On startup, the cluster compares the placement strings of each server to optimize the distribution of the partitions. See the voltdb command reference page for details.

A Wireshark plugin for analyzing the network connections between VoltDB servers and clients is now available from the VoltDB github repository. The plugin is provided “as is” as a courtesy to our users. See the included README for more information.

The new LN() function returns the natural logarithm of a numeric value. You can also use LOG() as a synonym for LN().

A new function, APPROX_COUNT_DISTINCT(), returns an approximation of the number of distinct values for a specified column expression. APPROX_COUNT_DISTINCT(expression) can be significantly faster and use less temporary memory than the corresponding COUNT(DISTINCT expression) function, especially when aggregating values across partitions.

The csvloader and kafkaloader utilities let you load data from external sources into a VoltDB database. By default, these utilities use INSERT statements to import the data, assuming there are no duplicates. However, you can now have these utilities use UPSERT to update existing records (or create new records where corresponding records do not exist) by including the --update flag. To use --update you must specify a table name rather than an input procedure and the table must have a primary key. See the csvloader and kafkaloader reference pages for details.

Another new flag for the csvloader utility is the --noquotechar tag. The --quotechar flag lets you specify the character for quoting values, which defaults to ASCII character 34, the quotation mark. The --noquotechar flag disables quoting and ensures the quotation mark is interpreted as a literal string character. Only the value separator and line delimiter then have special meaning in the input stream.

The configuration and startup of database replication (DR) have been simplified. The listen=”true” attribute is no longer needed on the <dr> tag in the deployment file — listening is enabled by default. Also, rather than editing the deployment file and performing a voltadmin update to clear the DR buffers, there is a single command, voltadmin dr reset, that can break replication and clear any pending logs on the master database. Finally, it is now possible to change the replica database's <connection> source attribute after the database has started. These improvements are reflected in the instructions for using DR in the Using VoltDB manual.

A number of changes and enhancements have been made to the JDBC interface to provide additional capabilities and better conformance with other JDBC implementations. Improvements include:

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

There were edge cases where certain SQL queries with outer joins of three or more tables could return incorrect answers. This problem has been fixed.

By default, query timeouts, as set by the JDBC setQueryTimeout function, are measured in seconds. However, it is now possible to define the timeout in more precise increments by changing the scale of the timeout function to milliseconds. You do this by adding the millisecond scale factor to the JDBC connection string. For example, the following code changes the timeout scale and then sets a timeout of 2500 millisecond (or 2.5 seconds):

Connection conn = DriverManager.getConnection(
    url + "?jdbc.querytimeout.unit=milliseconds");
            
Statement query = conn.createStatement();
query.setQueryTimeout(2500);

VoltDB supports a DECIMAL datatype with a fixed scale of 12. Previously passing a decimal value with a scale greater than 12 to VoltDB resulted in a run-time error. This behavior has changed and VoltDB now rounds values with a scale greater than 12 to the closest 12 decimal places.

It is now possible to debug VoltDB client applications and stored procedures using Eclipse. Please see the VoltDB Github wiki for instructions.

The requirement that a view definition contain a GROUP BY clause has been removed. It is now possible to create views containing aggregate functions, such as COUNT(*) , MAX(), MIN(), and SUM() without a GROUP BY clause. See the description of the CREATE VIEW statement in the Using VoltDB manual for details.

This release adds the MOD() function, which performs a modulo operation on two integer values. The first argument is the dividend and the second is the divisor and the function returns the remainder of dividing the first by the second. For example MOD(12,5) returns the value 2. See the Using VoltDB manual for details.

The behavior of Admin Mode has been changed. Previously, a database in Admin Mode rejected all requests on the client port. Now Admin Mode operates as a read-only mode for the database. All write requests on the client port are rejected, but read-only transactions (and read-only system procedures) are allowed. As before, both read-only and read/write transactions are allowed on the admin port.

The @Statistics system procedure supports a new selector, COMMANDLOG, which returns information about the status of command logging on the database cluster. See the discussion of @Statistcs in the Using VoltDB manual for details.

The web-based management tool, VoltDB Management Center, continues to be extended and enhanced. New features of the Management Center in this release include:

Several optimizations have been applied to database replication (DR) to improve overall performance and reliability, including compression of the binary logs. Users of V5.3 are strongly encouraged to upgrade, as the current release corrects a known issue with V5.3 related to restarting DR after a system crash or maintenance window.

Subquery support has been refined to improve reliability in a number of edge cases. Upgrading is strongly recommended for customers using subqueries in their applications.

VoltDB now interprets numeric constants containing a decimal point but not in E notation, such as "456.123", as DECIMAL values. Previously VoltDB interpreted such constants as floating point values. This change is being made for consistency with the SQL standard and other SQL implementations. To specify a floating point constant, use E notation (e.g. "4.56123e2").

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

Previously it was possible to use subqueries in the FROM clause of a SELECT statement. Now subqueries are supported in many more situations. Scalar subqueries, which return a single value, can be used in most cases where SQL functions can be used. Non-scalar subqueries, which return multiple rows or multiple columns per row, can be used in array comparisons and in the IN and EXISTS predicates.

Subqueries are valid only in the SELECT statement. They cannot be used in other SQL statements or index definitions. Also, for the initial release of extended subquery support, only replicated tables can be used in subqueries outside of the FROM clause.

The VoltDB Management Center contains a number of improvements and new capabilities, including:

When processing ad hoc queries that use parameters and placeholders (rather than a single SQL statement as a text string), VoltDB now makes use of previously cached queries to significantly improve performance for repeated queries. This can be most notable for JDBC prepared statements that are implemented as ad hoc queries with parameters.

The python client library has been updated to support SHA-256 hashing of passwords when authenticating to servers with security enabled.

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

There was in issue in earlier releases where, if the target of export or database replication (DR) stalled, the sending cluster buffers queued data to disk. However, this did not properly free the associated memory; and so memory usage would increase. It was possible, if the service buffered data to disk for an extended period of time, that the server process could run out of memory.

This issue has been resolved and memory associated with data buffered to disk is released appropriately. Note however, that even if excessive memory usage is no longer a problem, you should always try to resolve issues with stalled downstream systems when using export or DR because buffered data could eventually exceed disk storage capacity.

The C++ client library has been updated to support SHA-256 hashing of passwords when authenticating to servers with security enabled. By default, the client supports past and present server versions by using SHA-1 hashing. However, when connecting to VoltDB 5.2 and later servers, you can use SHA-256 hashing by specifying the hash type in the client configuration. For example:

voltdb::ClientConfig config("myusername", 
                            "mypassword", 
                            voltdb::HASH_SHA256);
voltdb::Client client = voltdb::Client::create(config);

Now both the Java and C++ client libraries support SHA-256 hashing. The new C++ client is available from the VoltDB client downloads page.

VoltDB 5.2 introduced use of SHA-2 hashing for authentication. This release brings the voltdb mask function up to date with the new authentication scheme. For customers using the mask function, be sure to re-hash your deployment file using the 5.2.1 voltdb mask command and use the newly hashed deployment file when starting the database to ensure all command utilities can authenticate properly.

Previously, database replication (DR) was able to continue despite individual node failures (in a K-safe environment). However failure of either the master or replica cluster would force a restart of DR. Beginning with 5.2, DR can resume across cluster failures when either the master or replica is recovered from command logs. See the chapter on "Database Replication" in the Using VoltDB manual for details.

The HTTP export connector now supports the use of Kerberos authentication when exporting to a WebHDFS endpoint that is configured to use Kerberos. See the section on using the HTTP export connector in the Using VoltDB manual for details.

VoltDB now supports partial indexes. That is, the index definition can contain a WHERE clause limiting the rows that are included in the index. For example:

CREATE INDEX completed_tasks 
    ON tasks (task_id, startdate, enddate)
    WHERE enddate IS NOT NULL;

For the initial release of partial indexes, there are certain limitations on when and where such indexes and the tables associated with them can be modified. For now, you cannot use the ALTER TABLE statement to modify a table with a partial index. This limitation is expected to be relaxed in a future release.

The Management Center, VoltDB's web-based management console, continues to be extended and improved. This release contains two major new features:

VoltDB now supports several new functions for performing bitwise operations on BIGINT values. The new functions support standard binary operands such as AND, OR, XOR, and NOT as well as bit shifting operations. See the reference pages for the BITAND(), BITNOT(), BITOR(), BITXOR(), BIT_SHIFT_LEFT(), and BIT_SHIFT_RIGHT() functions in the Using VoltDB manual for details.

Another new function, HEX(), converts a BIGINT value into its hexadecimal representation as a string. See the reference page for the HEX() function in the Using VoltDB manual for details.

VoltDB now supports SHA-2 hashing of credentials between the Java and c++ client libraries and the server. When you pass a username and password, the updated client library uses a SHA-2 hash of the credentials. On the server side, the VoltDB server accepts both SHA-1 (sent by previous versions of the client) and SHA-2. So both current and previous versions of the client libraries continue to work with the latest server release.

The VoltDB command line utility, voltadmin, now supports the stop command. The voltadmin stop command stops the VoltDB server process on the specified node. Note that the stop command can only be used on a K-safe cluster and will not intentionally shutdown the database. That is, the command will only stop a node if there are enough nodes left for the cluster to remain viable.

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

When database replication starts, a snapshot is sent from the master database to the replica. In this release several I/O improvements have been made to improve the performance and reliability of the initial DR snapshot.

There was an issue with how multiple buffers were grouped and managed in DR, which could result in decreased replication throughput. This issue has been resolved.

Changes in VoltDB 5.1 introduced a process that, when the database was idle, would "spin" making it appear that the database was consuming significant CPU cycles. When the database was active processing queries, the CPU usage would drop to normal levels.

Although not dangerous, this behavior was misleading and is corrected by the current update.

Database Replication (DR) lets you automatically copy updates to database tables from one database (the master) to another (the replica). Starting with VoltDB 5.1, DR has been rewritten to remove any single point of failure, improve performance, and allow new capabilities in the future. New features include:

For existing DR customers, the new capabilities and the elimination of the DR agent do necessitate some operational changes. Specifically, you must now:

See the chapter on Database Replication in the Using VoltDB manual for details.

VoltDB now allows you to export data to more than one target at a time. By assigning export tables to individual streams and then configuring each stream separately in the deployment file, you can export data to multiple targets simultaneously. For example, you might export deduped sensor data to Hadoop once it has been processed and export alerts regarding unusual events to HTTP for distribution via SMS, email, or other notification service. See the chapter on exporting live data in the Using VoltDB manual for details.

Use of multiple streams does require additional information in the schema and the deployment file. For example, the EXPORT TABLE statement now requires a TO STREAM clause so you can specify the stream to which each export table is directed. However, for backwards compatibility, the old syntax is still supported temporarily to allow customers time to migrate existing applications at their convenience.

VoltDB 5.0 introduced interactive DDL, eliminating the need for a precompiled application catalog. However, large schema could take a significant time to process interactively. VoltDB 5.1 solves this problem by allowing you to batch DDL statements. If you have your DDL statements in a single file, you can use the file --batch directive in sqlcmd to batch process the DDL statements. For example:

$ sqlcmd
1> file --batch myschema.sql;

If you have a mix of DDL (data definition language) statements and DML (data manipulation language) and directives you can batch process only the DDL statements by enclosing them in a file --inlinebatch directive and the specified end marker. For example:

load classes myprocs.jar;
file --inlinebatch END_OF_BATCH
CREATE PROCEDURE FROM CLASS procs.AddEmp;
CREATE PROCEDURE FROM CLASS procs.ChangeDept;
PARTITION PROCEDURE AddEmp ON TABLE emp COLUMN empid;
PARTITION PROCEDURE ChangeDept ON TABLE emp COLUMN empid;
END_OF_BATCH

Batch processing DDL statements can speed up the processing of those statements by a factor of 10 or more, depending on the number and complexity of the statements and the size of the cluster.

VoltDB Management Center, the web-based console for managing and monitoring a VoltDB database, now has a tab for administrative functions. On the Admin tab, you can pause and resume the database, save and restore snapshots, as well as review and update the database configuration. If security is enabled for the database, only users with the ADMIN permission can see and use the Admin tab in the Management Center.

In addition to the new features and capabilities described above, the following limitations in previous versions have been resolved:

There was an issue in earlier releases where using an INSERT INTO SELECT statement with an export table as the target for the insert either generated a null pointer exception or did not insert the expected data into the export stream. The issue only applies to INSERT INTO SELECT as an ad hoc query or within a multi-partitioned stored procedure.

These issues have now been corrected.

There was an issue in previous versions (starting with VoltDB 4.8), where if a query runs for a significant amount of time, VoltDB attempts to log a warning. However, the warning generates an error (index out of bounds) and stops the database.

This issue is now fixed.

In the original 5.0 release, any sqlcmd input line beginning with "file" (regardless of upper or lowercase) was interpreted as a file directive, even in the middle of a multi-line statement. This would happen, for example, if a CREATE TABLE statement included a column name starting with "file":

CREATE TABLE archive (
   ID INTEGER,
   Directory VARCHAR(128),
   Filename VARCHAR(128)
);

This usually resulted in several errors and the intended statement not being interpreted correctly. This issue is now fixed.

The major new feature in VoltDB 5.0 is the ability to enter data definition language (DDL) statements interactively. For example, using sqlcmd on the command line or the VoltDB Management Center SQL Query interface. This makes the process of creating a database and defining the schema more flexible. As part of the support for interactive DDL, the following features have been added:

Pleased note that processing DDL interactively can take longer than compiling an application catalog all at once. This is most noticeable when processing a large schema and especially on a multi-node cluster (where each change must be coordinated among the servers).

If you find entering DDL interactively too slow, it is possible to revert to precompiling the schema before starting the database. You have two choices:

Performance improvements for processing large schemas interactively are expected in upcoming releases.

The LIMIT PARTITION ROWS constraint now supports an EXECUTE clause that lets you specify a DELETE statement that is executed when the constraint value is exceeded. The EXECUTE clause gives you the ability to automatically "prune" older data when the constraint is reached. See the description of the CREATE TABLE statement in the Using VoltDB manual for details.

The HTTP connector, now supports Apache HttpFS (Hadoop HDFS over HTTP) servers as a target when exporting using the WebHDFS protocol. Set the export property httpfs.enable to "true" when exporting to HttpFS servers.

It is now possible to use the ORDER BY clause with LIMIT and/or OFFSET when performing a DELETE operation. ORDER BY allows you to more selectively remove database rows. For example, the following DELETE query removes the five oldest records, based on a timestamp column:

DELETE FROM events ORDER BY event_time ASC LIMIT 5;

Note that DELETE queries that include the ORDER BY clause must be single-partitioned and the ORDER BY clause must be deterministic. See the description of the DELETE statement in the Using VoltDB manual for details.

In addition to the new features listed above, VoltDB V5.0 includes fixes to several known issues:

There is an issue where, if the command log contains schema changes (performed through interactive DDL statements, voltadmin update, or @UpdateApplicationCatalog), when the command logs are recovered, the previous deployment file settings are used, even if an alternate deployment file is specified on the voltdb recover command line. Then, after recovering the database, a new schema update can result in the deployment settings specified on the command line taking affect.

Until this issue is resolved, the safest workaround to ensure the desired configuration is achieved is to perform the voltdb recover operation without modifying the current deployment file, then make deployment changes with the voltadmin update command after the database has started.

To ensure complete and accurate restoration of a database, recovery using command logs can only be performed to a cluster with the same number of unique partitions as the cluster that created the logs. If you restart and recover to the same cluster with the same deployment options, there is no problem. But if you change the deployment options for number of nodes, sites per host, or K-safety, recovery may not be possible.

For example, if a four node cluster is running with four sites per host and a K-safety value of one, the cluster has two copies of eight unique partitions (4 X 4 / 2). If one server fails, you cannot recover the command logs from the original cluster to a new cluster made up of the remaining three nodes, because the new cluster only has six unique partitions (3 X 4 / 2). You must either replace the failed server to reinstate the original hardware configuration or otherwise change the deployment options to match the number of unique partitions. (For example, increasing the site per host to eight and K-safety to two.)

VoltDB reserves the subfolder "segments" under the command log directory for storing the actual command log files. Do not add, remove, or modify any files in this directory. In particular, do not set the command log snapshot directory to a subfolder "segments" of the command log directory, or else the server will hang on startup.

Because DR data is buffered on the master database and then delivered asynchronously to the replica, there is always the danger that data does not reach the replica if a master node stops. This situation is mitigated in a K-safe environment by all copies of a partition buffering on the master cluster. Then if a sending node goes down, another node on the master database can take over sending logs to the replica. However, if multiple nodes go down and rejoin in rapid succession, it is possible that some buffered DR data — from transactions when one or more nodes were down — could be lost when another node with the last copy of that buffer also goes down.

If this occurs and the replica recognizes that some binary logs are missing, DR stops and must be restarted.

To avoid this situation, especially when cycling through nodes for maintenance purposes, the key is to ensure that all buffered DR data is transmitted before stopping the next node in the cycle. You can do this using the @Statistics system procedure to make sure the last ACKed timestamp (using @Statistitcs DR on the master cluster) is later than the timestamp when the previous node completed its rejoin operation.

Part of the replication process for XDCR is to verify that the record's starting and ending states match on both clusters, otherwise known as conflict resolution. To do that, XDCR must find the record first. Finding uniquely indexed records is efficient; finding non-unique records is not and can impact overall database performance.

To make you aware of possible performance impact, VoltDB issues a warning if you declare a table as a DR table and it does not have a unique index.

You cannot start XDCR if both databases already have data in the DR tables. Only one of the two participating databases can have preexisting data when DR starts for the first time.

When starting XDCR for the first time, where one database already contains data, a snapshot of that data is sent to the other database. While receiving and processing that snapshot, the receiving database is paused. That is, it is in read-only mode. Once the snapshot is completed and the two database are synchronized, the receiving database is automatically unpaused, resuming normal read/write operations.

Normally, XDCR will automatically restart where it left off after one of the clusters stops and recovers from its command logs (using the voltdb recover command). However, if the workload is predominantly multi-partition write transactions, a failed cluster may not be able to restart XDCR after it recovers. In this case, XDCR must be restarted from scratch, using the content from one of the clusters as the source for synchronizing and recreating the other cluster (using the voltdb create command) without any content in the DR tables.

When using XDCR, if the binary log from one cluster includes a TRUNCATE TABLE statement and the other cluster performs any write operation to the same table before the binary log is processed, the TRUNCATE TABLE operation will be reported as a conflict. Note that currently DELETE operations always supercede other actions, so the TRUNCATE TABLE will be executed on both clusters.

It is possible to place a limit on the number of rows that any partition can hold for a specific table using the LIMIT PARTITION ROWS clause of the CREATE TABLE statement. When close to the limit, transactions on either or both clusters can exceed the limit simultaneously, resulting in a potentially large number of delete operations that then generate conflicts when the the associated binary log reaches the other cluster.

VoltDB provides a way to generate a deterministically unique ID within a stored procedure using the getUniqueId method. This method guarantees uniqueness within the current cluster. However, the method could generate the same ID on two distinct database clusters. Consequently, when using XDCR, you should combine the return values of VoltProcedure.getUniqueId with VoltProcedure.getClusterId, which returns the current cluster's unique DR ID, to generate IDs that are unique across all clusters in your environment.

A bug in the Apache Kafka client can result in file descriptors being allocated but not released if the producer.type attribute is set to "sync" (which is the default). The consequence is that the system eventually runs out of file descriptors and the VoltDB server process will crash.

Until this bug is fixed, use of synchronous Kafka export is not recommended. The workaround is to set the Kafka producer.type attribute to "async" using the VoltDB export properties.

If, while Kafka import is enabled, the Kafka broker that VoltDB is connected to stops (for example, if the server crashes or is taken down for maintenance), some messages may be lost between Kafka and VoltDB. To ensure no data is lost, we recommend you disable VoltDB import before taking down the associated Kafka broker. You can then re-enable import after the Kafka broker comes back online.

When entering a multi-line statement at the sqlcmd prompt, if a line ends in a comment (indicated by two hyphens) and the comment contains an unmatched single quote character, the following lines of input are not interpreted correctly. Specifically, the comment is incorrectly interpreted as continuing until the next single quote character or a closing semi-colon is read. This is most likely to happen when reading in a schema file containing comments. This issue is specific to the sqlcmd utility.

A fix for this condition is planned for an upcoming point release

VoltDB currently intercepts assertions as part of its handling of stored procedures. Attempts to use assertions in stored procedures for debugging or to find programmatic errors will not work as expected.

The UPPER() and LOWER() functions return a string converted to all uppercase or all lowercase letters, respectively. However, for the initial release, these functions only operate on characters in the ASCII character set. Other case-sensitive UTF-8 characters in the string are returned unchanged. Support for all case-sensitive UTF-8 characters will be included in a future release.

There is a problem with how the math library used to build the C++ client library handles large decimal values on 32-bit operating systems. As a result, the C++ library cannot serialize and pass Decimal datatypes reliably on these systems.

Note that the C++ client interface can send and receive Decimal values properly on 64-bit platforms.

Normally, manual snapshots (those created with the Take a Snapshot button) are copied to the management server. However, if automated snapshots are also being created and copied to the management server, it is possible for an automated snapshot to override the manual snapshot.

If this happens, the workaround is to turn off automated snapshots (and their copying) temporarily. To do this, uncheck the box for copying snapshots, set the frequency to zero, and click OK. Then re-open the Edit Snapshots dialog and take the manual snapshot. Once the snapshot is complete and copied to the management server (that is, the manual snapshot appears in the list on the dialog box), you can re-enable copying and automated snapshots.

When the Enterprise Manager starts, it unpacks files that the web server uses into a subfolder of the /tmp directory. It does not delete these files when it stops. Under normal operation, this is not a problem. However, if you upgrade to a new version of the Enterprise Edition, files for the new version become intermixed with the older files and can result in the Enterprise Manager starting databases using the wrong version of VoltDB. To avoid this situation, make sure these temporary files are deleted before starting a new version of VoltDB Enterprise Manager.

The /tmp directory is emptied every time the server reboots. So the simplest workaround is to reboot your management server after you upgrade VoltDB. Alternately, you can delete these temporary files manually by deleting the winstone subfolders in the /tmp directory:

$ rm -vr /tmp/winstone*

When upgrading VoltDB Enterprise Edition, please note that the configuration files for the Enterprise Manager are not upwardly compatible. New product features may make existing database and/or deployment definitions unusable. It is always a good idea to delete existing configuration information before upgrading. You can delete the configuration files by deleting the ~/.voltdb directory. For example:

$ rm -vr ~/.voltdb

In the past, it was possible to run two (or more) databases on a single physical server by defining two logical servers with the same IP address and making the ports for each database unique. However, as a result of internal optimizations introduced in VoltDB 2.7, this technique no longer works when using the Enterprise Manager.

We expect to correct this limitation in a future release. Note that it is still possible to start multiple databases on a single server manually using the VoltDB shell commands.

Starting with VoltDB 5.1, database replication (DR) has changed and the VoltDB Enterprise Manager can no longer correctly configure, start or manage a replica database. The recommended method is to start the database manually and use the builtin VoltDB Management Center to manage the database by connecting to the cluster nodes directly on the HTTP port (8080 by default).

Any time the database schema or stored procedures are changed, the data table showing stored procedure statistics at the bottom of the Monitor section of the VOltDB Management Center get reset. As soon as new invocations of the stored procedures occur, the statistics table will show new values based on performance after the schema update. Until invocations occur, the procedure table is blank.

The ASSUMEUNIQUE attribute is designed for identifying columns in partitioned tables where the column values are known to be unique but the table is not partitioned on that column, so VoltDB cannot verify complete uniqueness across the database. Using interactive DDL, you can create a table with a column marked as ASSUMEUNIQUE, but if you try to partition the table on the ASSUMEUNIQUE column, you receive an error. The solution is to drop and add the column using the UNIQUE attribute instead of ASSUMEUNIQUE.

You cannot add or remove a column constraint such as UNIQUE or ASSUMEUNIQUE using the ALTER TABLE ALTER COLUMN statement. Instead to add or remove such constraints, you must first drop then add the modified column. For example:

ALTER TABLE employee DROP COLUMN empID;
ALTER TABLE employee ADD COLUMN empID INTEGER UNIQUE;

For partitioned tables, the value of the column used to partition the table determines what partition the row belongs to. If you use UPDATE to change this value and the new value belongs in a different partition, the UPDATE request will fail and the stored procedure will be rolled back.

Updating the partition column value may or may not cause the record to be repartitioned (depending on the old and new values). However, since you cannot determine if the update will succeed or fail, you should not use UPDATE to change the value of partitioning columns.

The workaround, if you must change the value of the partitioning column, is to use both a DELETE and an INSERT statement to explicitly remove and then re-insert the desired rows.

If you refer to a table or column name that does not exist, the VoltDB compiler issues the error message "user lacks privilege or object not found". This can happen, for example, if you misspell a table or column name.

Another situation where this occurs is if you mistakenly use double quotation marks to enclose a string literal (such as WHERE ColumnA="True"). ANSI SQL requires single quotes for string literals and reserves double quotes for object names. In the preceding example, VoltDB interprets "True" as an object name, cannot resolve it, and issues the "user lacks privilege" error.

The workaround is, if you receive this error, to look for misspelled table or columns names or string literals delimited by double quotes in the offending SQL statement.

VoltDB opens a file descriptor for every client connection to the database. In normal operation, this use of file descriptors is transparent to the user. However, if there are an inordinate number of concurrent client connections, or clients open and close many connections in rapid succession, it is possible for VoltDB to exceed the process limit on file descriptors. When this happens, new connections may be rejected or other disk-based activities (such as snapshotting) may be disrupted.

In environments where there are likely to be an extremely large number of connections, you should consider increasing the operating system's per-process limit on file descriptors.

VoltDB uses a number of different ports for interprocess communication as well as features such as HTTP access, DR, and so on. Port scanning software often interferes with normal operation of such ports by sending bogus data to them in an attempt to identify open ports.

VoltDB has hardened its port usage to ignore unexpected or irrelevant data from port scanners. However, the ports used for Database Replication (DR) cannot be protected in this way. So, in V4.6, a Java property was introduced to allow you to disable the DR ports, for situations where port scanning cannot be avoided. To disable the DR ports, set the Java property VOLTDB_DISABLE_DR to true before starting the database process. For example:

$ export VOLTDB_OPTS="-DVOLTDB_DISABLE_DR=true"
$ voltdb create myapplication.jar \
                --deployment=deployment.xml \
                --host=voltsvr1

Note that, if you disable the DR ports, you cannot use the database as a master for database replication.