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Note MySQL handling of BLOB

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Sean Corfield 2020-03-31 11:58:45 -07:00
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commit 2574e7e37f
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CHANGELOG.md
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@ -6,6 +6,7 @@ Only accretive/fixative changes will be made from now on.
The following changes have been made to **master** since the 1.0.409 build:
* In **Tips & Tricks**, noted that MySQL returns `BLOB` columns as `byte[]` instead of `java.sql.Blob`.
* 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.

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doc/tips-and-tricks.md
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@ -4,7 +4,7 @@ This page contains various tips and tricks that make it easier to use `next.jdbc
## CLOB & BLOB SQL Types
Columns declared with the `CLOB` or `BLOB` SQL types are typically rendered into Clojure result sets as database-specific custom types but they will implement `java.sql.Clob` or `java.sql.Blob` (as appropriate). In general, you can only read the data out of those Java objects during the current transaction, which effectively means that you need to do it either inside the reduction (for `plan`) or inside the result set builder (for `execute!` or `execute-one!`). If you always treat these types the same way for all columns across the whole of your application, you could simply extend `next.jdbc.result-set/ReadableColumn` to `java.sql.Clob` (and/or `java.sql.Blob`). Here's an example for reading `CLOB` into a `String`:
Columns declared with the `CLOB` or `BLOB` SQL types are typically rendered into Clojure result sets as database-specific custom types but they should implement `java.sql.Clob` or `java.sql.Blob` (as appropriate). In general, you can only read the data out of those Java objects during the current transaction, which effectively means that you need to do it either inside the reduction (for `plan`) or inside the result set builder (for `execute!` or `execute-one!`). If you always treat these types the same way for all columns across the whole of your application, you could simply extend `next.jdbc.result-set/ReadableColumn` to `java.sql.Clob` (and/or `java.sql.Blob`). Here's an example for reading `CLOB` into a `String`:
```clojure
(extend-protocol rs/ReadableColumn
@ -36,6 +36,8 @@ No helper or column reader is provided for `BLOB` data since it is expected that
Consult the [java.sql.Blob documentation](https://docs.oracle.com/javase/8/docs/api/java/sql/Blob.html) for more ways to process it.
> Note: the standard MySQL JDBC driver seems to return `BLOB` data as `byte[]` instead of `java.sql.Blob`.
## MS SQL Server
In MS SQL Server, the generated key from an insert comes back as `:GENERATED_KEYS`.