Storage Model

Hybrid

Although the original Ingres was row-based, Actian has incorporated columnar storage into its latest version of Ingres (Actian X) to improve its performance on OLAP tasks.

Storage Architecture

Disk-oriented

Although it is currently branded as the "Actian Hybrid", the "Hybrid" refers to its capability of performing both OLTP and OLAP tasks by employing a hybrid storage model (i.e. both row and column), not that it has a hybrid storage architecture. It is still disk oriented.

Checkpoints

Consistent Blocking

Ingres supports two types of checkpointing: online and offline. Offline checkpointing requires all users to disconnect from the database. It acquires a global lock on the entire database and performs backup on all the data. Online checkpointing does not require users to disconnect and is the default checkpointing scheme. Therefore, it is faster than offline checkpointing as it results in less down-time. However, it is still blocking. Users cannot proceed until the Ingres creates a consistent point of the database. The DBMS records all changes in the database but does not support operations such as drop or create during online checkpointing.

Query Compilation

Stored Procedure Compilation

Ingres allows users to write stored procedures in one of the supported query languages.

Views

Materialized Views

Ingres produces materialized views.

Storage Organization

Heaps Indexed Sequential Access Method (ISAM)

Heaps and ISAM are supported by Ingres.

Data Model

Relational

Ingres is a relational database system.

Query Execution

Materialized Model

Ingres executes queries by producing materialized views.

Logging

Logical Logging Physical Logging Command Logging

Query Interface

Custom API SQL Stored Procedures Command-line / Shell QUEL

Ingres was originally built on UNIX, hence it supports a command-line interface. It also supports SQL and QUEL and stored procedures in these two query languages. In addition, applications can use OpenAPI, a set of APIs in the C programming language, to interact with Ingres.

Stored Procedures

Supported

Ingres supports stored procedures in both SQL and QUEL.

Concurrency Control

Multi-version Concurrency Control (MVCC) Deterministic Concurrency Control Two-Phase Locking (Deadlock Detection)

Ingres uses the terms "logical lock" and "physical lock" to refer to transaction locks and latches, respectively. It supports multiversion concurrency control (MVCC). Its available lock levels are, from most to least granular, are Row, MVCC, Page, Table, Database.

It supports the following lock modes: NL(no lock), IS(intent to share), IX(intent to update), S(shared), SIX(shared with intent to update), and X(exclusive access). The locks in Ingres are managed by a lock manager. They are tracked using their unique lock IDs.

It supports deadlock detection and aborts one of the transactions that are deadlocked.

Indexes

B+Tree Hash Table R-Tree

One can create an index on an existing table in Ingres using the CREATE INDEX command. An index cannot contain more than 32 columns, but one can create as many indexes as needed on a table. Ingres chooses ISAM (Index Sequential Access Method) as the index data structure by default, but also supports B+ Tree, Hash Table, and R-Tree for this purpose. It can also create secondary indexes. In addition, it can create an index in parallel to reduce the time needed.

System Architecture

Shared-Everything

Ingres is a single-node database management system, and therefore it is "Share-Everything".

Foreign Keys

Supported

After primary keys are created, a user can create foreign keys using the New Foreign Key Dialog.

Isolation Levels

Read Uncommitted Read Committed Serializable Repeatable Read

Ingres supports four isolation levels, from favoring consistency to maximizing concurrency: Serializable, Repeatable Read, Read Committed. and Read Uncommitted, Serializable is the default isolation level because it provides the strongest consistency guarantee.

Compression

Null Suppression

Ingress's compression of tables only work on character and text columns. Trailing nulls and blanks are compressed. Non-nullable types such as Integer, floating point, and date are not compressed. It is not mentioned in the documentation that Ingres supports other types of compression schemes. Compression is applied to each page independently. It is shown in both the documentation and the original paper that compression in Ingres is useful in storing variable length domains. For example, if there is a column storing customer's reviews on a local business, then each review is padding at the end with nulls if it is shorter than the maximum allowed length to maintain homogeneity across the column. By applying compression on this column, these trailing nulls are compressed and the reviews take much less disk space because most of them are expected to be shorter than the maximum allowed length. However, the documentation suggests that compression should be used situationally, as decompression consumes CPU resources. It is up to the application to weight the trade-off between CPU utilization and disk space.

Joins

Nested Loop Join Hash Join Sort-Merge Join

Ingres supports hash join, sort-merge join, and nested loop join algorithms.