Query parameters and transactions

notes.md

@@ -0,0 +1,9 @@
+Results
+    * Postgres: Query a returns PGresult struct with all information that's
+    contents are valid as long as the struct exists, even after the connection
+    is closed. Can simply return unique pointer. Supports random access.
+
+    * SQLite: Retrieve one row at a time from the prepared statement object. No
+    random access, forward only. Can't even return a result object since a
+    second query of the same prepared statement will lose the state of the old
+    result.

src/postgres/lib.rs

@@ -4,6 +4,7 @@ use std::ptr;
 use std::libc::{c_void, c_char, c_int};
 use std::cast;
 use std::iterator::RandomAccessIterator;
+use std::vec;
 
 mod ffi {
     use std::libc::{c_char, c_int, c_uchar, c_uint, c_void};
@@ -37,12 +38,14 @@ mod ffi {
         fn PQclear(result: *PGresult);
         fn PQprepare(conn: *PGconn, stmtName: *c_char, query: *c_char,
                      nParams: c_int, paramTypes: *Oid) -> *PGresult;
+        fn PQdescribePrepared(conn: *PGconn, stmtName: *c_char) -> *PGresult;
         fn PQexecPrepared(conn: *PGconn, stmtName: *c_char, nParams: c_int,
                           paramValues: **c_char, paramLengths: *c_int,
                           paramFormats: *c_int, resultFormat: c_int)
                           -> *PGresult;
         fn PQntuples(result: *PGresult) -> c_int;
         fn PQnfields(result: *PGresult) -> c_int;
+        fn PQnparams(result: *PGresult) -> c_int;
         fn PQcmdTuples(result: *PGresult) -> *c_char;
         fn PQgetvalue(result: *PGresult, row_number: c_int, col_number: c_int)
                       -> *c_char;
@@ -116,7 +119,7 @@ impl<'self> PostgresConnection<'self> {
         let name = fmt!("__libpostgres_stmt_%u", id);
         self.next_stmt_id.put_back(id + 1);
 
-        let res = unsafe {
+        let mut res = unsafe {
             let raw_res = do query.as_c_str |c_query| {
                 do name.as_c_str |c_name| {
                     ffi::PQprepare(self.conn, c_name, c_query,
@@ -126,29 +129,65 @@ impl<'self> PostgresConnection<'self> {
             PostgresResult {result: raw_res}
         };
 
-        match res.status() {
+        if res.status() != ffi::PGRES_COMMAND_OK {
-            ffi::PGRES_COMMAND_OK =>
+            return Err(res.error());
-                Ok(~PostgresStatement {conn: self, name: name}),
+        }
-                _ => Err(res.error())
+
+        res = unsafe {
+            let raw_res = do name.as_c_str |c_name| {
+                ffi::PQdescribePrepared(self.conn, c_name)
+            };
+            PostgresResult {result: raw_res}
+        };
+
+        if res.status() != ffi::PGRES_COMMAND_OK {
+            return Err(res.error());
+        }
+
+        Ok(~PostgresStatement {conn: self, name: name,
+                               num_params: res.num_params()})
+    }
+
+    pub fn update(&self, query: &str, params: &[~str]) -> Result<uint, ~str> {
+        do self.prepare(query).chain |stmt| {
+            stmt.update(params)
         }
     }
 
-    pub fn update(&self, query: &str) -> Result<uint, ~str> {
+    pub fn query(&self, query: &str, params: &[~str])
+                 -> Result<~PostgresResult, ~str> {
         do self.prepare(query).chain |stmt| {
-            stmt.update()
+            stmt.query(params)
         }
     }
 
-    pub fn query(&self, query: &str) -> Result<~PostgresResult, ~str> {
+    pub fn in_transaction<T>(&self,
-        do self.prepare(query).chain |stmt| {
+                             blk: &fn(&PostgresConnection) -> Result<T, ~str>)
-            stmt.query()
+                             -> Result<T, ~str> {
+        match self.update("BEGIN", []) {
+            Ok(_) => (),
+            Err(err) => return Err(err)
+        };
+
+        // If the task fails in blk, the transaction will roll back when the
+        // connection closes
+        let ret = blk(self);
+
+        // TODO What to do about errors here?
+        if ret.is_ok() {
+            self.update("COMMIT", []);
+        } else {
+            self.update("ABORT", []);
         }
+
+        ret
     }
 }
 
 pub struct PostgresStatement<'self> {
     priv conn: &'self PostgresConnection<'self>,
-    priv name: ~str
+    priv name: ~str,
+    priv num_params: uint
 }
 
 #[unsafe_destructor]
@@ -165,11 +204,19 @@ impl<'self> Drop for PostgresStatement<'self> {
 }
 
 impl<'self> PostgresStatement<'self> {
-    fn exec(&self) -> Result<~PostgresResult, ~str> {
+    fn exec(&self, params: &[~str]) -> Result<~PostgresResult, ~str> {
+        if params.len() != self.num_params {
+            return Err(~"Incorrect number of parameters");
+        }
+
         let res = unsafe {
             let raw_res = do self.name.as_c_str |c_name| {
-                ffi::PQexecPrepared(self.conn.conn, c_name, 0, ptr::null(),
+                do as_c_str_array(params) |c_params| {
-                                    ptr::null(), ptr::null(), ffi::TEXT_FORMAT)
+                    ffi::PQexecPrepared(self.conn.conn, c_name,
+                                        self.num_params as c_int,
+                                        c_params, ptr::null(), ptr::null(),
+                                        ffi::TEXT_FORMAT)
+                }
             };
             ~PostgresResult{result: raw_res}
         };
@@ -182,14 +229,14 @@ impl<'self> PostgresStatement<'self> {
         }
     }
 
-    pub fn update(&self) -> Result<uint, ~str> {
+    pub fn update(&self, params: &[~str]) -> Result<uint, ~str> {
-        do self.exec().chain |res| {
+        do self.exec(params).chain |res| {
             Ok(res.affected_rows())
         }
     }
 
-    pub fn query(&self) -> Result<~PostgresResult, ~str> {
+    pub fn query(&self, params: &[~str]) -> Result<~PostgresResult, ~str> {
-        do self.exec().chain |res| {
+        do self.exec(params).chain |res| {
             Ok(res)
         }
     }
@@ -224,6 +271,10 @@ impl PostgresResult {
             None => 0
         }
     }
+
+    fn num_params(&self) -> uint {
+        unsafe { ffi::PQnparams(self.result) as uint }
+    }
 }
 
 impl Container for PostgresResult {
@@ -236,6 +287,14 @@ impl PostgresResult {
     pub fn iter<'a>(&'a self) -> PostgresResultIterator<'a> {
         PostgresResultIterator {result: self, next_row: 0}
     }
+
+    pub fn get<'a>(&'a self, idx: uint) -> PostgresRow<'a> {
+        if idx >= self.len() {
+            fail!("Out of bounds access");
+        }
+
+        self.iter().idx(idx).get()
+    }
 }
 
 pub struct PostgresResultIterator<'self> {
@@ -287,18 +346,36 @@ impl<'self> Container for PostgresRow<'self> {
 }
 
 impl<'self, T: FromStr> Index<uint, Option<T>> for PostgresRow<'self> {
-    fn index(&self, index: &uint) -> Option<T> {
+    fn index(&self, idx: &uint) -> Option<T> {
-        if *index >= self.len() {
+        self.get(*idx)
+    }
+}
+
+impl<'self> PostgresRow<'self> {
+    pub fn get<T: FromStr>(&self, idx: uint) -> Option<T> {
+        if idx >= self.len() {
             fail!("Out of bounds access");
         }
 
         let s = unsafe {
             let raw_s = ffi::PQgetvalue(self.result.result,
                                         self.row as c_int,
-                                        *index as c_int);
+                                        idx as c_int);
             str::raw::from_c_str(raw_s)
         };
 
         FromStr::from_str(s)
     }
 }
+
+fn as_c_str_array<T>(array: &[~str], blk: &fn(**c_char) -> T) -> T {
+    let mut c_array: ~[*c_char] = vec::with_capacity(array.len() + 1);
+    foreach s in array.iter() {
+        // DANGER, WILL ROBINSON
+        do s.as_c_str |c_s| {
+            c_array.push(c_s);
+        }
+    }
+    c_array.push(ptr::null());
+    blk(vec::raw::to_ptr(c_array))
+}

src/postgres/test.rs

@@ -12,17 +12,39 @@ macro_rules! chk(
 )
 
 #[test]
-fn test_conn() {
+fn test_basic() {
+    let conn = chk!(PostgresConnection::new("postgres://postgres@localhost"));
+
+    do conn.in_transaction |conn| {
+        chk!(conn.update("CREATE TABLE basic (id INT PRIMARY KEY)", []));
+        chk!(conn.update("INSERT INTO basic (id) VALUES (101)", []));
+
+        let res = chk!(conn.query("SELECT id from basic WHERE id = 101", []));
+        assert_eq!(1, res.len());
+        let rows: ~[PostgresRow] = res.iter().collect();
+        assert_eq!(1, rows.len());
+        assert_eq!(1, rows[0].len());
+        assert_eq!(Some(101), rows[0][0]);
+
+        Err::<(), ~str>(~"")
+    };
+}
+
+#[test]
+fn test_params() {
 	let conn = chk!(PostgresConnection::new("postgres://postgres@localhost"));
 
-    chk!(conn.update("DROP TABLE IF EXISTS foo"));
+    do conn.in_transaction |conn| {
-    chk!(conn.update("CREATE TABLE foo (foo INT PRIMARY KEY)"));
+        chk!(conn.update("CREATE TABLE basic (id INT PRIMARY KEY)", []));
-    chk!(conn.update("INSERT INTO foo (foo) VALUES (101)"));
+        chk!(conn.update("INSERT INTO basic (id) VALUES ($1)", [~"101"]));
 
-    let res = chk!(conn.query("SELECT foo from foo"));
+        let res = chk!(conn.query("SELECT id from basic WHERE id = $1", [~"101"]));
-    assert_eq!(1, res.len());
+        assert_eq!(1, res.len());
-    let rows: ~[PostgresRow] = res.iter().collect();
+        let rows: ~[PostgresRow] = res.iter().collect();
-    assert_eq!(1, rows.len());
+        assert_eq!(1, rows.len());
-    assert_eq!(1, rows[0].len());
+        assert_eq!(1, rows[0].len());
-    assert_eq!(Some(101), rows[0][0]);
+        assert_eq!(Some(101), rows[0][0]);
+
+        Err::<(), ~str>(~"")
+    };
 }