Select Cypher version

modules/ROOT/content-nav.adoc

@@ -6,6 +6,7 @@
 * xref:queries/index.adoc[]
 ** xref:queries/concepts.adoc[]
 ** xref:queries/basic.adoc[]
+** xref:queries/select-version.adoc[]
 ** xref:queries/composed-queries/index.adoc[]
 *** xref:queries/composed-queries/combined-queries.adoc[]
 *** xref:queries/composed-queries/conditional-queries.adoc[]

modules/ROOT/pages/queries/index.adoc

@@ -6,6 +6,7 @@ It also discusses how to compose combined queries using `UNION` and conditional
 
 * xref:queries/concepts.adoc[]
 * xref:queries/basic.adoc[]
+* xref:queries/select-version.adoc[]
 * xref:queries/composed-queries/index.adoc[]
 ** xref:queries/composed-queries/combined-queries.adoc[]
 ** xref:queries/composed-queries/conditional-queries.adoc[] label:new[Introduced in Neo4j 2025.06]

modules/ROOT/pages/queries/select-version.adoc

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+:description: Information about how to select Cypher version for queries or databases.
+
+= Select Cypher version
+
+Users can specify the version of Cypher in which they want to run their queries, choosing between Cypher 5 and Cypher 25.
+The Cypher version can be set for individual queries or as the default language for a database.
+
+[[cypher-versions-explained]]
+== Cypher 5, Cypher 25, and Neo4j explained
+
+Starting in 2025, the Neo4j server transitioned to a calendar-based versioning system.
+This means Neo4j will no longer use its previous semantic versioning and release pattern (e.g., 5_25, 5.26).
+Instead, releases from 2025 onwards will follow a *YYYY.MM* format, beginning with version 2025.01 released in January 2025, followed by 2025.02 released in February 2025, and so on.
+
+Cypher 25 is introduced alongside Neo4j 2025.06.
+However, users running Neo4j version 2025.06 or later can choose to run their queries using the previous version of Cypher: Cypher 5.
+If so, Neo4j will use Cypher as it existed at the time of the Neo4j **TBC** release.
+
+[IMPORTANT]
+All new databases created after the release of 2025.06 will continue to use Cypher 5 as their default language.
+To change the default language, see xref:queries/select-version.adoc#alter-default-cypher-version[Alter the default Cypher version for a database].
+See also xref:queries/select-version.adoc#config-database-upgrades[Cypher versions, configuration settings, and DBMS upgrades] for information about what default Cypher version is used when upgrading a DBMS.
+
+For information about updates to Cypher in different Neo4j versions, see xref:deprecations-additions-removals-compatibility.adoc[].
+For information about Cypher 5, see the link:https://neo4j.com/docs/cypher-manual/5/introduction/[Cypher 5 Manual].
+
+[[selection-query-cypher-version]]
+== Select the Cypher version for queries
+
+To select the Cypher version of a query, prepend it with `CYPHER <language version>`. 
+
+Selecting `CYPHER 5` ensures that the query will be executed using the language as it existed at the time of the Neo4j **TBC** release.
+Any changes introduced after the **TBC** release will not affect the query.
+
+Selecting `CYPHER 25` ensures that the query will be executed using the language as it exists in the version of Neo4j that the database is currently running, provided it is on Neo4j 2025.06 or later.
+
+Below are two examples showing the two versions of Cypher behaving differently.
+
+.Differences in setting properties between Cypher 5 and Cypher 25
+======
+The first query uses a `RELATIONSHIP` instead of `MAP` on the right-hand side of a xref:clauses/set.adoc[`SET`] clause.
+This was allowed in Cypher 5, but disallowed in Cypher 25, which requires that the xref:functions/scalar.adoc#functions-properties[`properties()`] function is used to get the map of properties from nodes or relationships before referencing them in a `SET` clause.
+
+.Setting properties on a node from a relationship using Cypher 5
+[source, cypher]
+----
+CYPHER 5
+MATCH (n:Order)-[r:SHIPPED_TO]->(:Address) 
+SET n = r
+----
+
+.Setting properties on a node from a relationship using Cypher 25
+[source, cypher]
+----
+CYPHER 25
+MATCH (n:Order)-[r:SHIPPED_TO]->(:Address)
+SET n = properties(r)
+----
+======
+
+.Differences in listing constraints between Cypher 5 and Cypher 25
+======
+In this example, the same statement listing the `name` and `type` of the xref:constraints/index.adoc[constraints] in a database is executed first using Cypher 5 and then with Cypher 25.
+Note that the return values in the `type` column have been updated in the results from the statement run with Cypher 25.
+
+////
+CREATE CONSTRAINT node_uniqueness_constraint
+FOR (n:Label) REQUIRE n.property IS UNIQUE;
+CREATE CONSTRAINT rel_uniqueness_constraint
+FOR ()-[r:REL_TYPE]-() REQUIRE r.property IS UNIQUE;
+////
+
+.Listing the constraint name and type values using Cypher 5
+[source, cypher]
+----
+CYPHER 5
+SHOW CONSTRAINTS YIELD name, type
+----
+
+.Result
+[role="queryresult",options="header,footer",cols="2*<m"]
+|===
+| name | type 
+
+| "node_uniqueness_constraint" | "UNIQUENESS"
+| "rel_uniqueness_constraint"  | "RELATIONSHIP_UNIQUENESS"
+
+2+d|Rows: 2
+|===
+
+.Listing the constraint name and type values using Cypher 25
+[source, cypher]
+----
+CYPHER 25
+SHOW CONSTRAINTS YIELD name, type
+----
+
+.Result
+[role="queryresult",options="header,footer",cols="2*<m"]
+|===
+| name | type 
+
+| "node_uniqueness_constraint" | "NODE_PROPERTY_UNIQUENESS"
+| "rel_uniqueness_constraint"  | "RELATIONSHIP_PROPERTY_UNIQUENESS"
+
+2+d|Rows: 2
+|===
+
+======
+
+If a database has specified a default Cypher version, it is possible to set a different Cypher version for individual queries.
+For example, if a database is created with Cypher 5 as its default language, prepending a query run on that database with `CYPHER 25` ensures the query uses Cypher 25.
+
+[[procedures-and-functions]]
+=== Procedures and functions
+
+link:{neo4j-docs-base-uri}/operations-manual/current/procedures[Procedures] and xref:functions/index.adoc[functions] (including built-in and link:{neo4j-docs-base-uri}/apoc/current/[APOC]) are tied to a specific Cypher language version.
+Therefore, procedures and functions in Neo4j 2025.06+ and APOC 2025.06+ (both of which have Cypher 25 as their default language) may behave differently depending on what version of Cypher is used.
+
+For example, APOC 2025.06 removed Cypher 25 support of the procedure `apoc.create.uuids()`, meaning it is not available to queries running Cypher 25.
+However, it can still be used on APOC 2025.06 if queries are prepended with `CYPHER 5`, or if the database’s default version is set to `CYPHER 5`.
+In this case, Neo4j will use APOC and Cypher as they existed at the time of the **TBC** release.
+
+.Using a procedure removed in Cypher 25 with APOC 2025.06+
+[source, cypher]
+----
+CYPHER 5
+CALL apoc.create.uuids(10)
+----
+
+[[cypher-selection-with-other-query-options]]
+=== Combine Cypher version selection with other query options
+
+It is possible to combine Cypher version selection with other xref:planning-and-tuning/query-tuning.adoc[query options].
+The below example selects both the version and the xref:planning-and-tuning/runtimes/concepts.adoc[runtime] of Cypher for the same query:
+
+.Combining Cypher version selection with other query options
+[source, cypher]
+----
+CYPHER 5 runtime=parallel
+MATCH (n:Person)
+RETURN n.name
+----
+
+[[select-default-cypher-version]]
+== Select the default Cypher version when creating a database
+
+Databases created on Neo4j 2025.06 or later will continue to have Cypher 5 as their default language (if {neo4j-docs-base-uri}/operations-manual/current/configuration/configuration-settings/#config_db.query.default_language[`config_db.query.default_language`] is set to `CYPHER 5` -- see  xref:queries/select-version.adoc#config-database-upgrades[Cypher versions, configuration settings, and DBMS upgrades] below).
+This is true for link:{neo4j-docs-base-uri}/operations-manual/current/database-administration/#manage-database-systems[system, standard, and composite] Neo4j databases.
+
+To select a different default Cypher version for a database, add `DEFAULT LANGUAGE <language version>` to the link:{neo4j-docs-base-uri}/operations-manual/current/database-administration/standard-databases/create-databases/[`CREATE DATABASE`] statement.
+This can be done on any Neo4j database.
+
+Selecting `CYPHER 5` as the default database language ensures that every query run on that database uses the language as it existed at the time of the Neo4j **TBC** release (unless a query is prepended with `CYPHER 25`, which overrides this default).
+Any changes introduced after the **TBC** release will not affect the semantics of the query.
+
+.Create a database with Cypher 5 as the default language
+[source, cypher]
+----
+CREATE DATABASE my_database DEFAULT LANGUAGE CYPHER 5
+----
+
+Selecting `CYPHER 25` ensures that the query will be executed using the language as it exists in the version of Neo4j that the database is currently running, provided it is on Neo4j 2025.06 or later (unless a query is prepended with `CYPHER 5`, which overrides this default).
+
+.Create a database with Cypher 25 as the default language
+[source, cypher]
+----
+CREATE DATABASE my_new_database DEFAULT LANGUAGE CYPHER 25
+----
+
+[[alter-default-cypher-version]]
+== Alter the default Cypher version for a database
+
+To alter the default Cypher version on a database, add `SET DEFAULT LANGUAGE <language version>` to the link:{neo4j-docs-base-uri}/operations-manual/current/database-administration/standard-databases/alter-databases/[`ALTER DATABASE`] command.
+
+[NOTE]
+Selecting a default Cypher version on a database requires the link:{neo4j-docs-base-uri}/operations-manual/current/authentication-authorization/dbms-administration/#access-control-dbms-administration-database-management[`SET DATABASE DEFAULT LANGUAGE`] privilege.
+
+.Set Cypher 5 as the default language on an existing database
+[source, cypher]
+----
+ALTER DATABASE my_new_database SET DEFAULT LANGUAGE CYPHER 5
+----
+
+.Set Cypher 25 as the default language on an existing database
+[source, cypher]
+----
+ALTER DATABASE my_database SET DEFAULT LANGUAGE CYPHER 25
+----
+
+[[show-cypher-versions]]
+== Show the Cypher version of databases
+
+The Cypher version of a database can be seen using the link:{neo4j-docs-base-uri}/operations-manual/current/database-administration/standard-databases/listing-databases/[`SHOW DATABASES`] command as follows:
+
+.Retrieve the default language on existing databases
+[source, cypher]
+----
+SHOW DATABASES YIELD name, defaultLanguage
+----
+
+[NOTE]
+`defaultLanguage` is not returned by default.
+It can only be returned with `YIELD`.
+For more information, see the link:{neo4j-docs-base-uri}/operations-manual/current/database-administration/standard-databases/listing-databases/#_show_databases_output[Operations Manual -> `SHOW DATABASES` output].
+
+.Result
+[role="queryresult",options="header,footer",cols="2*<m"]
+|===
+| name | defaultLanguage 
+
+| "my_database" | "CYPHER 25"
+| "my_new_database"  | "CYPHER 5"
+| "system"           | "CYPHER 25"
+
+2+d|Rows: 3
+|===
+
+[[config-database-upgrades]]
+== Cypher versions, configuration settings, and DBMS upgrades
+
+Changing the Cypher version of new databases in a DBMS can also be done with the setting link:{neo4j-docs-base-uri}/operations-manual/current/configuration/configuration-settings/#config_db.query.default_language[`config_db.query.default_language`] (default value: `CYPHER_5`).
+This setting determines the default language for new databases where it has not been specified as part of a `CREATE` or `ALTER` database command.
+For example, `config_db.query.default_language=CYPHER_25` will set Cypher 25 as the default language for a DBMS.
+For more information about using configuration settings, see the link:{neo4j-docs-base-uri}/operations-manual/current/configuration/[Operations Manual -> Configuration].
+
+The table below outlines which Cypher version is assigned to databases in different upgrade or installation scenarios:
+
+[cols="3", options="header"]
+|===
+| Scenario | `db.query.default_language` | Databases
+
+| *Standard DBMS upgrade to Neo4j 2025.06+*
+| Unset
+| *Existing system database:* `CYPHER_5` +
+*Existing user databases:* `CYPHER_5` +
+*New user databases default:* `CYPHER_5`
+
+| *Custom DBMS upgrade to Neo4j 2025.06+*
+| Manually set to `CYPHER_25` by administrator
+| *Existing system database:* `CYPHER_5` +
+*Existing user databases:* `CYPHER_5`  +
+*New user databases default:* `CYPHER_25`
+
+| *New installation of Neo4j 2025.06+* 
+| Set to `CYPHER_5`
+| *New system database:* `CYPHER_5` +
+*New user databases default:* `CYPHER_5`
+
+|===
+
+For more information about upgrading and migrating Neo4j databases, see the link:{neo4j-docs-base-uri}/upgrade-migration-guide/current/[Upgrade and migration guide].