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//! Code examples for the usage of this database driver. //! //! # 1. Database connections //! //! Establish an authenticated connection to the database server //! (see also [`ConnectParams`](../struct.ConnectParams.html)): //! //! ```rust,no_run //! use hdbconnect::{Connection, IntoConnectParams}; //! # use hdbconnect::HdbResult; //! # fn foo() -> HdbResult<()> { //! let params = "hdbsql://my_user:my_passwd@the_host:2222".into_connect_params()?; //! let mut connection = Connection::new(params)?; //! # Ok(()) //! # } //! ``` //! //! # 2. Queries and other database calls //! //! ## 2.1 Generic method: Connection.statement() and HdbResponse() //! //! The most generic way to fire SQL statements without preparation is using //! `Connection::statement()`. //! This generic method can handle very different kinds of calls (queries, dml, procedures), //! and thus has the most complex return type, `HdbResponse`. //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! let query = "SELECT foo FROM bar"; //! # #[allow(unused_variables)] //! let response = connection.statement(query)?; // HdbResponse //! # Ok(()) //! # } //! ``` //! //! `HdbResponse` is a nested enum which covers all possible //! return values we can get from the database. //! You thus have to analyze it to come to the //! concrete response relevant for your call. //! You can do this either explicitly using `match` etc or with the //! adequate short-cut method, e.g.: //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let query = "SELECT foo FROM bar"; //! let response = connection.statement(query)?; // HdbResponse //! # #[allow(unused_variables)] //! let resultset = response.into_resultset()?; // ResultSet //! # Ok(()) //! # } //! ``` //! //! You can do the same of course with `HdbResponse`s obtained from the execution //! of prepared statements. //! //! ## 2.2 More specific methods with tailored return values //! //! In many cases it will be more appropriate and convenient to use one of the //! specialized methods //! //! * `connection.query(...) // ResultSet` //! * `connection.dml(...) // usize` //! * `connection.exec(...) // ()` //! //! where each has an adequate simple result type: //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! let qry = "SELECT foo FROM bar"; //! let resultset = connection.query(qry)?; // ResultSet //! # Ok(()) //! # } //! ``` //! //! ## 2.3 Prepared statements //! //! With prepared statements, the code will look like this: //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! let stmt_str = "insert into TEST_PREPARE (F_STRING, F_INTEGER) values(?, ?)"; //! let mut stmt = connection.prepare(stmt_str)?; //! stmt.add_batch(&("foo", 45_i32))?; //! stmt.add_batch(&("bar", 46_i32))?; //! stmt.execute_batch()?; //! # Ok(()) //! # } //! ``` //! //! Or like this: //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! let stmt_str = "select NAME, CITY from TEST_TABLE where age > ?"; //! let mut stmt = connection.prepare(stmt_str)?; //! stmt.add_batch(&(45_i32))?; //! let resultset = stmt.execute_batch()?.into_resultset()?; //! # Ok(()) //! # } //! ``` //! //! # 3. Result set evaluation //! //! # 3.1 Iterating over rows //! //! Evaluating a result set by iterating over the rows explicitly is possible, of course. //! Note that the row iterator returns `HdbResult<Row>`, not `Row`, //! because the result set might need to fetch more rows lazily from the server, which can fail. //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = ""; //! # let resultset = connection.query(qry)?; //! for row in resultset { //! let row = row?; //! // now you have a real row //! } //! # Ok(()) //! # } //! ``` //! //! Such a streaming-like behavior is especially appropriate for large result sets. //! Iterating over the rows, while they are fetched on-demand from the server in smaller portions, //! makes it easy to write complex evaluations in an efficient and scalable manner. //! //! ```ignore //! let key_figure = resultset.into_iter()?.map(|r|{r?}).filter(...).fold(...); //! ``` //! //! # 3.2 Explicitly evaluating a single row //! //! You _can_ retrieve the field values of a row individually, in arbitrary order. //! `hdbconnect::Row` provides for this a single //! method that is generalized by its return value, //! so you need to specify the target type explicitly: //! //! ```rust,no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams, Row}; //! # fn main() { } //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = ""; //! # let resultset = connection.query(qry)?; //! for row in resultset { //! let mut row:Row = row?; //! # #[allow(unused_variables)] //! let f1: String = row.next_value().unwrap().try_into()?; //! # #[allow(unused_variables)] //! let f2: Option<i32> = row.next_value().unwrap().try_into()?; //! # #[allow(unused_variables)] //! let f3: i32 = row.next_value().unwrap().try_into()?; //! # #[allow(unused_variables)] //! let f4: chrono::NaiveDateTime = row.next_value().unwrap().try_into()?; //! } //! # Ok(()) //! # } //! ``` //! //! # 3.3 Direct conversion of entire rows //! //! A usually more convenient way is to convert the complete row into a normal rust value //! or tuple or struct: //! //! ```rust,no_run //! # use serde_derive::Deserialize; //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn main() { } //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = ""; //! # let resultset = connection.query(qry)?; //! #[derive(Deserialize)] //! struct TestData {/* ...*/} //! let qry = "select * from TEST_RESULTSET"; //! for row in connection.query(qry)? { //! let td: TestData = row?.try_into()?; //! } //! # Ok(()) //! # } //! ``` //! //! As hdbconnect uses return type polymorphism for this conversion (based on `serde`), //! you need to specify the type of your target variable explicitly. //! //! # 3.4 Direct conversion of entire result sets //! //! Even more convenient is the option to convert the complete result set in a single step. //! Depending on the concrete numbers of rows and columns, this option supports //! a variety of target data structures. //! //! # 3.4.1 Matrix-structured result sets //! //! You can always, and __most often want to__, use a <code>Vec</code> of a struct or //! tuple that matches the fields of the result set. //! //! ```rust,no_run //! # use serde_derive::Deserialize; //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn main() { } //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = ""; //! #[derive(Deserialize)] //! struct MyRow {/* ...*/} //! //! # #[allow(unused_variables)] //! let result: Vec<MyRow> = connection.query(qry)?.try_into()?; //! # Ok(()) //! # } //! ``` //! //! # 3.4.2 Single-line result sets //! //! If the result set contains only a single line (e.g. because you specified //! TOP 1 in your select, or you qualified the full primary key), //! then you can choose to deserialize into a plain <code>`MyRow`</code> directly. //! //! ```rust,no_run //! # use serde_derive::Deserialize; //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn main() { } //! # fn foo() -> HdbResult<()> { //! # let params = "hdbsql://my_user:my_passwd@the_host:2222".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = "SELECT foo FROM bar"; //! # #[derive(Deserialize)] //! # struct MyRow {/* ...*/} //! let result: MyRow = connection.query(qry)?.try_into()?; //! # Ok(()) //! # } //! ``` //! //! # 3.4.3 Single-column result sets //! //! If the result set contains only a single column, then you can choose to //! deserialize into a <code>Vec<field></code>, //! where <code>field</code> is a type that matches the field of the result set. //! If a plain rust type is used, you don't even need to derive Deserialize: //! //! ```rust, no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = ""; //! let result: Vec<u32> = connection.query(qry)?.try_into()?; //! # Ok(()) //! # } //! ``` //! //! # 3.4.4 Single-value result sets //! //! If the result set contains only a single value (one row with one column), //! then you can also deserialize into a plain <code>field</code>: //! //! ```rust, no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let mut connection = Connection::new(params)?; //! # let qry = ""; //! let result: u32 = connection.query(qry)?.try_into()?; //! # Ok(()) //! # } //! ``` //! //! # 4. Deserialization of field values //! //! The deserialization of individual values provides flexibility without data loss: //! //! * You can e.g. convert values from a nullable column into a plain field, //! provided that no NULL values are given in the result set. //! //! * Vice versa, you can use an Option<code><field></code> as target structure, //! even if the column is marked as NOT NULL. //! //! * Source and target integer types can differ from each other, //! as long as the concrete values can be assigned without loss. //! //! * You can convert numeric values on-the-fly into default String representations. //! //! You should use this flexibility with some care though, or you will face errors //! when the data violates the boundaries of the target values. //! //! //! # 5. Binary Values //! //! So far, specialization support is not yet in rust stable. Without that, you have to use //! [`serde_bytes::Bytes`](https://docs.serde.rs/serde_bytes/struct.Bytes.html) and //! [`serde_bytes::ByteBuf`](https://docs.serde.rs/serde_bytes/struct.ByteBuf.html) //! as lean wrappers around `&[u8]` and `Vec<u8>` //! to serialize into or deserialize from binary database types. //! //! ```ignore //! let raw_data: Vec<u8> = ...; //! insert_stmt.add_batch(&(Bytes::new(&*raw_data)))?; //! ``` //! //! //! ```rust, no_run //! # use hdbconnect::{Connection, ResultSet, HdbResult, IntoConnectParams}; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let qry = ""; //! # let mut connection = Connection::new(params)?; //! # let resultset: ResultSet = connection.query(qry)?; //! let bindata: serde_bytes::ByteBuf = resultset.try_into()?; // single binary field //! let first_byte = bindata[0]; //! # Ok(()) //! # } //! ``` //! //! //! # 6. LOBs //! Binary and Character LOBs can be treated like "normal" binary and String data, i.e. //! you can convert them with the methods described above into `ByteBuf` or String values. //! //! You can avoid materializing the complete "Large Object", e.g. //! if you want to stream it into a writer: //! //! ```rust, no_run //! # use hdbconnect::{Connection, HdbResult, IntoConnectParams, ResultSet}; //! # use hdbconnect::types::NCLob; //! # fn foo() -> HdbResult<()> { //! # let params = "".into_connect_params()?; //! # let query = ""; //! # let mut connection = Connection::new(params)?; //! # let mut resultset: ResultSet = connection.query(query)?; //! # let mut writer: Vec<u8> = vec![]; //! let mut row = resultset.next_row()?.unwrap(); //! let mut nclob: NCLob = row.next_value().unwrap().try_into_nclob()?; //! std::io::copy(&mut nclob, &mut writer)?; //! # Ok(()) //! # } //! ``` //! //! While being read by `io::copy()`, the NCLOB will continuously fetch more data from the //! database until the complete NCLOB is processed. //!