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Surface database metadata handling in Getting Started

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Sean Corfield 2020-04-10 12:07:08 -07:00
parent 2fd27d18bd
commit f70d93b156
2 changed files with 16 additions and 1 deletions
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2
CHANGELOG.md
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@ -10,7 +10,7 @@ The following changes have been made to **master** since the 1.0.409 build:
* Fixes #102 by allowing keywords or strings in `:return-keys`.
* Fixes #101 by tightening the spec on a JDBC URL to correctly reflect that it must start with `jdbc:`.
* Add support for calling `.getLoginTimeout`/`.setLoginTimeout` on the reified `DataSource` returned by `get-datasource` when called on a hash map "db-spec" or JDBC URL string.
* Documentation improvements based on feedback (mostly from Slack).
* Documentation improvements based on feedback (mostly from Slack), including a section on database metadata near the end of **Getting Started**.
## Stable Builds

15
doc/getting-started.md
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@ -365,6 +365,21 @@ If you are working with Java Time, some JDBC drivers will automatically convert
> Note: `next.jdbc.date-time` also provides functions you can call to enable automatic conversion of SQL date/timestamp types to Clojure data types when reading result sets. If you need specific conversions beyond that to happen automatically, consider extending the `ReadableColumn` protocol, mentioned above.
## Processing Database Metadata
JDBC provides several features that let you introspect the database to obtain lists of tables, views, and so on. `next.jdbc` does not provide any specific functions for this but you can easily get this metadata from a `java.sql.Connection` and turn it into Clojure data as follows:
```clojure
(with-open [con (p/get-connection ds opts)]
(-> (.getMetaData con) ; produces java.sql.DatabaseMetaData
;; return a java.sql.ResultSet describing all tables and views:
(.getTables nil nil nil (into-array ["TABLE" "VIEW"]))
(rs/datafiable-result-set ds opts)))
```
Several methods on `DatabaseMetaData` return a `ResultSet` object, e.g., `.getCatalogs()`, `.getClientInfoProperties()`, `.getSchemas()`.
All of those can be handled in a similar manner to the above. See the [Oracle documentation for `java.sql.DatabaseMetaData`](https://docs.oracle.com/en/java/javase/11/docs/api/java.sql/java/sql/DatabaseMetaData.html) (Java 11) for more details.
## Support from Specs
As you are developing with `next.jdbc`, it can be useful to have assistance from `clojure.spec` in checking calls to `next.jdbc`'s functions, to provide explicit argument checking and/or better error messages for some common mistakes, e.g., trying to pass a plain SQL string where a vector (containing a SQL string, and no parameters) is expected.