next.jdbc Options

This section documents all of the options that are supported by all of the functions in next.jdbc. Nearly every function accepts an optional hash map as the last argument, that can control many of the behaviors of the library.

The most general options are described first, followed by more specific options that apply only to certain functions.

Datasources and Connections

Although get-datasource does not accept options, the "db spec" hash map passed in may contain the following options:

• :dbtype -- a string that identifies the type of JDBC database being used,
• :dbname -- a string that identifies the name of the actual database being used,
• :dbname-separator -- an optional string that can be used to override the / or : that is normally placed in front of the database name in the JDBC URL,
• :host -- an optional string that identifies the IP address or hostname of the server on which the database is running; the default is "127.0.0.1"; if :none is specified, next.jdbc will assume this is for a local database and will omit the host/port segment of the JDBC URL,
• :host-prefix -- an optional string that can be used to override the // that is normally placed in front of the IP address or hostname in the JDBC URL,
• :port -- an optional integer that identifies the port on which the database is running; for common database types, next.jdbc knows the default so this should only be needed for non-standard setups or "exotic" database types,
• :classname -- an optional string that identifies the name of the JDBC driver class to be used for the connection; for common database types, next.jdbc knows the default so this should only be needed for "exotic" database types,
• :user -- an optional string that identifies the database username to be used when authenticating,
• :password -- an optional string that identifies the database password to be used when authenticating.

Any additional keys provided in the "db spec" will be passed to the JDBC driver as Properties when each connection is made. Alternatively, when used with next.jdbc.connection/->pool, additional keys correspond to setters called on the pooled connection object.

If you are using HikariCP and next.jdbc.connection/->pool to create a connection pooled datasource, you need to provide :username for the database username (instead of, or as well as, :user).

Any path that calls get-connection will accept the following options:

• :auto-commit -- a Boolean that determines whether operations on this connection should be automatically committed (the default, true) or not; note that setting :auto-commit false is commonly required when you want to stream result set data from a query (along with fetch size etc -- see below),
• :read-only -- a Boolean that determines whether the operations on this connection should be read-only or not (the default, false).
• :connection -- a hash map of camelCase properties to set on the Connection object after it is created; these correspond to .set* methods on the Connection class and are set via the Java reflection API (using org.clojure/java.data). If :autoCommit or :readOnly are provided, they will take precedence over the fast, specific options above.

If you need additional options set on a connection, you can either use Java interop to set them directly, or provide them as part of the "db spec" hash map passed to get-datasource (although then they will apply to all connections obtained from that datasource).

Note: If plan, execute!, or execute-one! are passed a DataSource, a "db spec" hash map, or a JDBC URL string, they will call get-connection, so they will accept the above options in those cases.

Generating SQL

Except for query (which is simply an alias for execute!), all the "friendly" SQL functions accept the following options (in addition to all the options that plan, execute!, and execute-one! can accept):

• :table-fn -- the quoting function to be used on the string that identifies the table name, if provided,
• :column-fn -- the quoting function to be used on any string that identifies a column name, if provided.

They also support a :suffix argument which can be used to specify a SQL string that should be appended to the generated SQL string before executing it, e.g., :suffix "FOR UPDATE".

In addition, find-by-keys accepts the following options (see its docstring for more details):

• :columns -- specify one or more columns to SELECT to override selecting all columns,
• :order-by -- specify one or more columns, on which to sort the results,
• :top / :limit / :offset / :fetch to support pagination of results.

In the simple case, the :columns option expects a vector of keywords and each will be processed according to :column-fn, if provided. A column alias can be specified using a vector pair of keywords and both will be processed according to :column-fn, e.g., [:foo [:bar :quux]] would expand to foo, bar AS quux. You can also specify the first element of the pair as a string which will be used as-is in the generated SQL, e.g., [:foo ["COUNT(*)" :total]] would expand to foo, COUNT(*) AS total. In the latter case, the alias keyword will still be processed according to :column-fn but the string will be untouched -- you are responsible for any quoting and/or other formatting that might be required to produce a valid SQL expression.

Note: get-by-id accepts the same options as find-by-keys but it will only ever produce one row, as a hash map, so sort order and pagination are less applicable, although :columns may be useful.

Generating Rows and Result Sets

Any function that might realize a row or a result set will accept:

• :builder-fn -- a function that implements the RowBuilder and ResultSetBuilder protocols; strictly speaking, plan and execute-one! only need RowBuilder to be implemented (and plan only needs that if it actually has to realize a row) but most generation functions will implement both for ease of use.
• :label-fn -- if :builder-fn is specified as one of next.jdbc.result-set's as-modified-* builders, this option must be present and should specify a string-to-string transformation that will be applied to the column label for each returned column name.
• :qualifier-fn -- if :builder-fn is specified as one of next.jdbc.result-set's as-modified-* builders, this option should specify a string-to-string transformation that will be applied to the table name for each returned column name. It will be called with an empty string if the table name is not available. It can be omitted for the as-unqualified-modified-* variants.

In addition, execute! accepts the :multi-rs true option to return multiple result sets -- as a vector of result sets.

Note: Subject to the caveats above about :builder-fn, that means that plan, execute!, execute-one!, and the "friendly" SQL functions will all accept these options for generating rows and result sets.

Statements & Prepared Statements

Any function that creates a Statement or a PreparedStatement will accept the following options (see below for additional options for PreparedStatement):

• :concurrency -- a keyword that specifies the concurrency level: :read-only, :updatable,
• :cursors -- a keyword that specifies whether cursors should be closed or held over a commit: :close, :hold,
• :fetch-size -- an integer that guides the JDBC driver in terms of how many rows to fetch at once; the actual behavior of specifying :fetch-size is database-specific: some JDBC drivers use a zero or negative value here to trigger streaming of result sets -- other JDBC drivers require this to be positive for streaming and may require additional options to be set on the connection as well,
• :max-rows -- an integer that tells the JDBC driver to limit result sets to this many rows,
• :result-type -- a keyword that affects how the ResultSet can be traversed: :forward-only, :scroll-insensitive, :scroll-sensitive,
• :timeout -- an integer that specifies the (query) timeout allowed for SQL operations, in seconds. See Handling Timeouts in Tips & Tricks for more details on this and other possible timeout settings.
• :statement -- a hash map of camelCase properties to set on the Statement or PreparedStatement object after it is created; these correspond to .set* methods on the Statement class (which PreparedStatement inherits) and are set via the Java reflection API (using org.clojure/java.data). If :fetchSize, :maxRows, or :queryTimeout are provided, they will take precedence over the fast, specific options above.

If you specify either :concurrency or :result-type, you must specify both of them. If you specify :cursors, you must also specify :result-type and :concurrency.

Note: For MS SQL Server to return table names (for qualified column names), you must specify :result-type with one of the scroll values (and so you must also specify :concurrency).

Any function that creates a PreparedStatement will additionally accept the following options:

• :return-keys -- a truthy value asks that the JDBC driver to return any generated keys created by the operation; it can be true or it can be a vector of keywords identifying column names that should be returned.

Not all databases or drivers support all of these options, or all values for any given option. If :return-keys is a vector of column names and that is not supported, next.jdbc will attempt a generic "return generated keys" option instead. If that is not supported, next.jdbc will fall back to a regular SQL operation. If other options are not supported, you may get a SQLException.

Note: If plan, execute!, or execute-one! are passed a DataSource, a "db spec" hash map, or a JDBC URL string, they will call prepare to create a PreparedStatement, so they will accept the above options in those cases.

In addition the the above, next.jdbc.prepare/execute-batch! (which does not create a PreparedStatement) accepts an options hash map that can also contain the following:

• :batch-size -- an integer that determines how to partition the parameter groups for submitting to the database in batches,
• :large -- a Boolean flag that indicates whether the batch will produce large update counts (long rather than int values).

Transactions

The transact function and with-transaction macro accept the following options:

• :isolation -- a keyword that identifies the isolation to be used for this transaction: :none, :read-committed, :read-uncommitted, :repeatedable-read, or :serializable; these represent increasingly strict levels of transaction isolation and may not all be available depending on the database and/or JDBC driver being used,
• :read-only -- a Boolean that indicates whether the transaction should be read-only or not (the default),
• :rollback-only -- a Boolean that indicates whether the transaction should commit on success (the default) or rollback.

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