The PostgreSQL Global Development Group announced yesterday its first beta release of PostgreSQL 12. It is now also available for download. This release contains previews of all features that will be available in the final release of PostgreSQL 12, though some details of the release could also change.
PostgreSQL 12 feature highlights
Indexing Performance, Functionality, and Management
PostgreSQL 12 will improve the overall performance of the standard B-tree indexes with improvements to the space management of these indexes as well. These improvements also provide a reduction of index size for B-tree indexes that are frequently modified, in addition to a performance gain.
Additionally, PostgreSQL 12 adds the ability to rebuild indexes concurrently, which lets you perform a REINDEX operation without blocking any writes to the index. This feature should help with lengthy index rebuilds that could cause downtime when managing a PostgreSQL database in a production environment.
PostgreSQL 12 extends the abilities of several of the specialized indexing mechanisms. The ability to create covering indexes, i.e. the INCLUDE clause that was introduced in PostgreSQL 11, has now been added to GiST indexes. SP-GiST indexes now support the ability to perform K-nearest neighbor (K-NN) queries for data types that support the distance (<->) operation.
The amount of write-ahead log (WAL) overhead generated when creating a GiST, GIN, or SP-GiST index is also significantly reduced in PostgreSQL 12, which provides several benefits to the disk utilization of a PostgreSQL cluster and features such as continuous archiving and streaming replication.
Inlined WITH queries (Common table expressions)
Common table expressions (or WITH queries) can now be automatically inlined in a query if they:
- a) are not recursive
- b) do not have any side-effects
- c) are only referenced once in a later part of a query
This removes an “optimization fence” that has existed since the introduction of the WITH clause in PostgreSQL 8.4
PostgreSQL 12 while processing tables with thousands of partitions for operations, it only needs to use a small number of partitions.
This release also provides improvements to the performance of both INSERT and COPY into a partitioned table. ATTACH PARTITION can now be performed without blocking concurrent queries on the partitioned table. Additionally, the ability to use foreign keys to reference partitioned tables is now permitted in PostgreSQL 12.
JSON path queries per SQL/JSON specification
PostgreSQL 12 now allows execution of JSON path queries per the SQL/JSON specification in the SQL:2016 standard. Similar to XPath expressions for XML, JSON path expressions let you evaluate a variety of arithmetic expressions and functions in addition to comparing values within JSON documents.
A subset of these expressions can be accelerated with GIN indexes, allowing the execution of highly performant lookups across sets of JSON data.
PostgreSQL 12 now supports case-insensitive and accent-insensitive comparisons for ICU provided collations, also known as “nondeterministic collations“. When used, these collations can provide convenience for comparisons and sorts, but can also lead to a performance penalty as a collation may need to make additional checks on a string.
Most-common Value Extended Statistics
CREATE STATISTICS, introduced in PostgreSQL 12 to help collect more complex statistics over multiple columns to improve query planning, now supports most-common value statistics. This leads to improved query plans for distributions that are non-uniform.
PostgreSQL 12 allows the creation of generated columns that compute their values with an expression using the contents of other columns. This feature provides stored generated columns, which are computed on inserts and updates and are saved on disk. Virtual generated columns, which are computed only when a column is read as part of a query, are not implemented yet.
Pluggable Table Storage Interface
PostgreSQL 12 introduces the pluggable table storage interface that allows for the creation and use of different methods for table storage. New access methods can be added to a PostgreSQL cluster using the CREATE ACCESS METHOD command and subsequently added to tables with the new USING clause on CREATE TABLE.
A table storage interface can be defined by creating a new table access method.
In PostgreSQL 12, the storage interface that is used by default is the heap access method, which is currently is the only built-in method.
The pg_verify_checkums command has been renamed to pg_checksums and now supports the ability to enable and disable page checksums across a PostgreSQL cluster that is offline. Previously, page checksums could only be enabled during the initialization of a cluster with initdb.
Authentication & Connection Security
GSSAPI now supports client-side and server-side encryption and can be specified in the pg_hba.conf file using the hostgssenc and hostnogssencrecord types. PostgreSQL 12 also allows for discovery of LDAP servers based on DNS SRV records if PostgreSQL was compiled with OpenLDAP.
Few noted behavior changes in PostgreSQL 12
There are several changes introduced in PostgreSQL 12 that can affect the behavior as well as management of your ongoing operations. A few of these are noted below; for other changes, visit the “Migrating to Version 12” section of the release notes.
- The recovery.conf configuration file is now merged into the main postgresql.conf file. PostgreSQL will not start if it detects thatrecovery.conf is present. To put PostgreSQL into a non-primary mode, you can use the recovery.signal and the standby.signal files.
You can read more about archive recovery here:
- Just-in-Time (JIT) compilation is now enabled by default.
- OIDs can no longer be added to user created tables using the WITH OIDs clause. Operations on tables that have columns that were created using WITH OIDS (i.e. columns named “OID”) will need to be adjusted.
Running a SELECT * command on a system table will now also output the OID for the rows in the system table as well, instead of the old behavior which required the OID column to be specified explicitly.
Testing for Bugs & Compatibility
The stability of each PostgreSQL release greatly depends on the community, to test the upcoming version with the workloads and testing tools in order to find bugs and regressions before the general availability of PostgreSQL 12. As this is a Beta, minor changes to database behaviors, feature details, and APIs are still possible. The PostgreSQL team encourages the community to test the new features of PostgreSQL 12 in their database systems to help eliminate any bugs or other issues that may exist.
This is the first beta release of version 12. The PostgreSQL Project will release additional betas as required for testing, followed by one or more release candidates, until the final release in late 2019. For further information please see the Beta Testing page.
Many other new features and improvements have been added to PostgreSQL 12. Please see the Release Notes for a complete list of new and changed features.