diesel 2.2.12

A safe, extensible ORM and Query Builder for PostgreSQL, SQLite, and MySQL
Documentation 
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#![allow(unsafe_code)] // ffi code
extern crate pq_sys;

use std::ffi::CString;
use std::os::raw as libc;
use std::ptr;

use super::result::PgResult;
use crate::pg::PgTypeMetadata;
use crate::result::QueryResult;

use super::raw::RawConnection;

enum StatementKind {
    Unnamed { sql: CString, param_types: Vec<u32> },
    Named { name: CString },
}

pub(crate) struct Statement {
    kind: StatementKind,
    param_formats: Vec<libc::c_int>,
}

impl Statement {
    pub(super) fn execute(
        &self,
        raw_connection: &mut RawConnection,
        param_data: &[Option<Vec<u8>>],
        row_by_row: bool,
    ) -> QueryResult<PgResult> {
        let params_pointer = param_data
            .iter()
            .map(|data| {
                data.as_ref()
                    .map(|d| d.as_ptr() as *const libc::c_char)
                    .unwrap_or(ptr::null())
            })
            .collect::<Vec<_>>();
        let param_lengths = param_data
            .iter()
            .map(|data| data.as_ref().map(|d| d.len().try_into()).unwrap_or(Ok(0)))
            .collect::<Result<Vec<_>, _>>()
            .map_err(|e| crate::result::Error::SerializationError(Box::new(e)))?;
        let param_count: libc::c_int = params_pointer
            .len()
            .try_into()
            .map_err(|e| crate::result::Error::SerializationError(Box::new(e)))?;

        match &self.kind {
            StatementKind::Named { name } => {
                unsafe {
                    // execute the previously prepared statement
                    // in autocommit mode, this will be a new transaction
                    raw_connection.send_query_prepared(
                        name.as_ptr(),
                        param_count,
                        params_pointer.as_ptr(),
                        param_lengths.as_ptr(),
                        self.param_formats.as_ptr(),
                        1,
                    )
                }?
            }
            StatementKind::Unnamed { sql, param_types } => unsafe {
                // execute the unnamed prepared statement using send_query_params
                // which internally calls PQsendQueryParams, making sure the
                // prepare and execute happens in a single transaction. This
                // makes sure these are handled by PgBouncer.
                // See https://github.com/diesel-rs/diesel/pull/4539
                raw_connection.send_query_params(
                    sql.as_ptr(),
                    param_count,
                    param_types.as_ptr(),
                    params_pointer.as_ptr(),
                    param_lengths.as_ptr(),
                    self.param_formats.as_ptr(),
                    1,
                )
            }?,
        };
        if row_by_row {
            raw_connection.enable_row_by_row_mode()?;
        }
        Ok(raw_connection.get_next_result()?.expect("Is never none"))
    }

    pub(super) fn prepare(
        raw_connection: &mut RawConnection,
        sql: &str,
        name: Option<&str>,
        param_types: &[PgTypeMetadata],
    ) -> QueryResult<Self> {
        let sql = CString::new(sql)?;
        let param_types_vec = param_types
            .iter()
            .map(|x| x.oid())
            .collect::<Result<Vec<_>, _>>()
            .map_err(|e| crate::result::Error::SerializationError(Box::new(e)))?;

        if let Some(name) = name {
            let name = CString::new(name)?;
            let param_count: libc::c_int = param_types
                .len()
                .try_into()
                .map_err(|e| crate::result::Error::SerializationError(Box::new(e)))?;
            let internal_result = unsafe {
                raw_connection.prepare(
                    name.as_ptr(),
                    sql.as_ptr(),
                    param_count,
                    param_types_to_ptr(Some(&param_types_vec)),
                )
            };
            PgResult::new(internal_result?, raw_connection)?;

            Ok(Statement {
                kind: StatementKind::Named { name },
                param_formats: vec![1; param_types.len()],
            })
        } else {
            // For unnamed statements, we'll return a Statement object without
            // actually preparing it. This allows us to use send_query_params
            // later in the execute call. This is needed to better interface
            // with PgBouncer which cannot handle unnamed prepared statements
            // when those are prepared and executed in separate transactions.
            // See https://github.com/diesel-rs/diesel/pull/4539
            Ok(Statement {
                kind: StatementKind::Unnamed {
                    sql,
                    param_types: param_types_vec,
                },
                param_formats: vec![1; param_types.len()],
            })
        }
    }
}

fn param_types_to_ptr(param_types: Option<&Vec<u32>>) -> *const pq_sys::Oid {
    param_types
        .map(|types| types.as_ptr())
        .unwrap_or(ptr::null())
}