6.7 Release Notes

The MemSQL 6.7 release is focused on usability, compatibility and performance. With respect to usability, we’ve made major enhancements in our toolset for deploying and managing MemSQL, understanding how tables are being used to help you tune your table structures, automatic sampling for improved query optimization, resource management, and more. Compatibility functions have been added for date handling and regular expression matching to make it easier to port queries from legacy databases. And performance of data loading and star join query processing have been improved dramatically.

Beginning with this release, MemSQL may be used free of charge in production for clusters with up to 128GB of total RAM capacity.

See the descriptions and changelog below for more information on these new features.

Query Execution

The following query execution features have been added:

  • Star join query execution performance has improved through addition of support for joining on integer columns in columnstore tables, using Intel Single-Instruction Multiple-Data (SIMD) instructions and operations directly on encoded (compressed) data. Some join/group by/aggregate queries have improved over 100X.
  • Faster filtering on columnstores
  • Improved IN-list filter performance

Query Optimization, Compilation and Statistics

The following query optimizations have been added in this release:

  • Cardinality estimation (CE) improvements for IN-lists using histograms
  • Fast histogram creation on row store tables with random sampled scan
  • Fast, accurate, uniform random sampling for complex predicates CE on row store tables using random sampled scan
  • interpret_first setting to improve ad hoc query (first run) query performance (experimental)
  • OPTION clause for global query options, applicable to SELECT, INSERT…SELECT, UPDATE, DELETE
  • Added warnings in EXPLAIN and information_schema for queries with comparisons between mismatched datatypes which may involve unsafe datatype conversions and/or degrade performance.
  • New management views (MV_QUERY_COLUMN_USAGE, MV_AGGREGATED_COLUMN_USAGE) to track how columns are used in queries to help with index tuning and application design
  • Improvements to query compilation speed

Functional Extensions

The following new functional capabilities are supported:

  • Dynamic SQL
  • Regular expression support for advanced regular expressions (ARE) and common Perl regular expression extensions. Added functions regexp_instr() and regexp_replace().
  • CUBE, ROLLUP, and GROUPING()
  • nvl(), to_char(), to_timestamp(), decode(), and strcmp() functions
  • APPROX_COUNT_DISTINCT_* functions based on HyperLogLog algorithm to allow persisting and rolling up approximate count distinct state for fast count distinct estimates
  • UNION/UNION ALL on the right side of IN
  • SELECT FOR UPDATE to allow lock stability between statements for online transaction processing workloads
  • MySQL binary protocol and prepared statements
  • Fast random sampled scans on row store tables using table_name WITH(sample_ratio = <value>)

Tools

  • Next generation of command-line tools that lay a foundation for flexible, efficient deployment and management of MemSQL clusters using industry-standard tools like Puppet, Chef, Ansible, and Salt
  • memsql-deploy tool for those who wish to deploy with the MemSQL-provided toolset
  • Fully-supported APT and YUM repositories for secure distribution of MemSQL packages. New toolchain is distributed and installed via the RPM and DEB file format.
  • memsql-toolbox, a stateless tool for administering MemSQL clusters, with performance and reliability improvements over the previous-generation memsql-ops tool
  • New customer portal providing a single point of access for license management, downloading MemSQL software, discussion forums, and support
  • MemSQL Studio graphical management console upgrades including 6.7 support and graphical EXPLAIN and PROFILE plan display

System Management

  • Resource governor extensions to control CPU usage and concurrency
  • Machine-learning-based workload management extensions to estimate resources used by queries the first time they are run and queue large queries appropriately to maintain throughput and response time under load
  • Management view to show columnstore merge status
  • Extensions to information_schema views to track status of statistics (last update and automatic statistics status)
  • Additional cluster events tracked in mv_events view
  • New MV_CLUSTER_STATUS_VIEW to give cluster status in query-able form
  • Added memory-related information to MV_NODES view

Data Loading, Backup and Restore

  • Adaptive data compression for LOAD DATA (up to 2X performance gain)
  • Tar backup to Amazon S3
  • Backup/restore to/from Azure Blob Store
  • Enhanced metadata for backups in MV_BACKUP_HISTORY view as well as backup files
  • Enhanced validation prior to restore or disaster recovery replicate operations, to ensure there is enough space on the target system
  • SELECT INTO OUTFILE on S3
  • JSON and Avro support for LOAD DATA and pipelines

Maintenance Release Changelog

2018-11-19 Version 6.7.3

  • Improved out-of-memory handling when retrieving autostats during query compilation.
  • Now allow SET SESSION autocommit = 0 commands against leaf nodes. Some MySQL clients will execute this statement when they connect, so disallowing it blocked users from connecting to leaves to monitor usage with clients that run this command. SET GLOBAL autocommit=0 remains blocked on leaf nodes. Disabling autocommit globally on leaves interferes with memsql’s ability to coordinate transactions.
  • Now block SELECT queries without FROM clauses from compiling when MemSQL memory use is nearing maximum_memory. Historically, SELECT queries with no FROM clauses were allowed to compile even if memory use was low as they played a part in cluster health checks that run against leaves. This is no longer the case, so there is no reason to risk compiling them when memory use it low.
  • The CRC32 builtin function was not returning results consistent with the crc32c algorithm when compared to the result produced by external libraries.
  • Fixed tracking of missing blobs at the end of recovery. Previously, finishing recovery of a slave database in the middle of a columnstore transaction could cause a missing blob to go untracked.
  • Added variable (enable_broadcast_left_join) to control whether the optimizer chooses the broadcast left join optimization.
  • Updated Brazilian time zones due to recent changes made by the country of Brazil. Specifically America/Campo_Grande, America/Cuiaba, and America/Sao_Paulo. Note: All Brazil/ time zones are deprecated.
  • Correctly block restoring an individual partition database backup on the master aggregator. Before this fix, the RESTORE command would fail but an empty reference database would be left behind that couldn’t be dropped. This fix also allows the left over empty reference database to be dropped if it had already been created before upgrading.
  • Now allow the memsqlctl configuration file path to be specified using the MEMSQLCTL_CONFIG environment variable.
  • Fixed bug in memsqlctl print-secure-key that caused it to incorrectly attempt writing the state file.

2018-11-06 Version 6.7.1

  • Initial GA release of MemSQL 6.7.
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