docs/_docs/sql/calcite-based-sql-engine.adoc

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= Calcite-Based SQL Engine

This Alpha release introduces new SQL engine based on the Apache Calcite framework to parse and optimize queries and generate execution plans. Previously, it was based on H2 Database.

Apache Calcite is a dynamic data management framework, which mainly serves for mediating between applications and one or more data storage locations and data processing engines.
For more information on Apache Calcite, please see the link:https://calcite.apache.org/docs/[product documentation,window=_blank].

Replacing H2 SQL engine with Apache Calcite incorporates the following general improvements:

* *Wider SQL support*: Apache Calcite, unlike H2, is specifically designed for SQL enablement on top of an arbitrary external data storage;
* *Better optimization algorithms*: Apache Calcite optimizes queries by repeatedly applying planner rules to a relational expression;
* *Higher overall performance*: Calcite offers much higher levels of execution flexibility, as well as higher efficiency in terms of both memory and CPU consumption.

== Data Manipulation Language (DML)

This section walks you through all data manipulation language (DML) commands supported by Apache Ignite Alpha 3.

WARNING: Currently, `WITH` and `MERGE` commands are not supported.

=== SELECT

Retrieves data from a table or multiple tables.

[source,sql]
----
SELECT [ hintComment ] [ STREAM ] [ ALL | DISTINCT ]
    { * | projectItem [, projectItem ]* }
FROM tableExpression
[ WHERE booleanExpression ]
[ GROUP BY { groupItem [, groupItem ]* } ]
[ HAVING booleanExpression ]
----

=== INSERT

Inserts data into a table.

[source,sql]
----
{ INSERT | UPSERT } INTO tablePrimary
[ '(' column [, column ]* ')' ]
query
----

=== UPDATE

Updates data in a table.

[source,sql]
----
UPDATE tablePrimary
SET assign [, assign ]*
[ WHERE booleanExpression ]
----

=== DELETE

Deletes data from a table.

[source,sql]
----
DELETE FROM tablePrimary [ [ AS ] alias ]
[ WHERE booleanExpression ]
----

== Supported Operators and Functions

=== Aggregate Functions

==== COUNT

[source,sql]
----
COUNT( [ ALL | DISTINCT ] value [, value ]*)
----

Returns the number of input rows for which value is not null (wholly not null if value is composite).

==== AVG

[source,sql]
----
AVG( [ ALL | DISTINCT ] numeric)
----

Returns the average (arithmetic mean) of numeric across all input values.

==== SUM

[source,sql]
----
SUM( [ ALL | DISTINCT ] numeric)
----

Returns the sum of numeric across all input values.

==== MIN

[source,sql]
----
MIN( [ ALL | DISTINCT ] value)
----

Returns the minimum value of value across all input values.

==== MAX

[source,sql]
----
MAX( [ ALL | DISTINCT ] value)
----

Returns the maximum value of value across all input values.

==== STRING_AGG

[source,sql]
----
STRING_AGG( value [, separator ] [ ORDER BY ...])
----

Concatenates the values of string expressions and places separator values between them.

==== STRING_CONCAT

[source,sql]
----
STRING_CONCAT(string1, string2, ... stringN)
----

Concatenates the text values in the specified data ranges.


=== Functions


==== JSON

* JSON_EXISTS
* JSON_VALUE
* JSON_QUERY
* JSON_OBJECT
* JSON_ARRAY
* JSON_PRETTY
* STRING
* CHAR_LENGTH
* CHARACTER_LENGTH
* UPPER
* LOWER
* POSITION
* TRIM
* OVERLAY
* SUBSTRING
* INITCAP
* SPACE
* STRCMP
* REVERSE
* REGEXP_REPLACE
* SHA1
* MD5
* LTRIM
* TO_BASE64
* FROM_BASE64
* COMPRESS
* CONCAT
* TRANSLATE
* ASCII
* LEFT
* RIGHT
* REPEAT
* SOUNDEX
* For more information on functions supported by Apache Calcite, see the link:https://calcite.apache.org/docs/reference.html#operators-and-functions[product documentation,window=_blank].

==== NUMERIC

* POWER
* ABS
* MOD
* SQRT
* LN
* LOG10
* EXP
* CEIL
* FLOOR
* RAND
* ACOS
* ASIN
* ATAN
* ATAN2
* CBRT
* COS
* COT
* DEGREES
* PI()
* RADIANS
* ROUND
* SIGN
* SIN
* TAN
* TRUNCATE
* CHR
* COSH
* SINH
* TANH
* For more information on functions supported by Apache Calcite, see the link:https://calcite.apache.org/docs/reference.html#operators-and-functions[product documentation,window=_blank].

==== GENERAL

* NULLIF
* COALESCE
* CAST
* NVL
* GREATEST
* For more information on functions supported by Apache Calcite, see the link:https://calcite.apache.org/docs/reference.html#operators-and-functions[product documentation,window=_blank].


==== TIMESTAMP

* TIMESTAMP_ADD
* TIMESTAMP_DIFF
* EXTRACT
* LAST_DAY
* For more information on functions supported by Apache Calcite, see the link:https://calcite.apache.org/docs/reference.html#operators-and-functions[product documentation,window=_blank].