diff --git a/core/Cargo.toml b/core/Cargo.toml
index 4ff68bc9..594ec4a0 100644
--- a/core/Cargo.toml
+++ b/core/Cargo.toml
@@ -9,7 +9,6 @@ enum-set = { git = "https://github.com/rnewman/enum-set" }
 failure = "0.1.1"
 indexmap = "1"
 lazy_static = "0.2"
-num = "0.1"
 ordered-float = { version = "0.5", features = ["serde"] }
 uuid = { version = "0.5", features = ["v4", "serde"] }
 serde = { version = "1.0", features = ["rc"] }
diff --git a/db/Cargo.toml b/db/Cargo.toml
index a356fb2c..f89121b7 100644
--- a/db/Cargo.toml
+++ b/db/Cargo.toml
@@ -14,7 +14,6 @@ indexmap = "1"
 itertools = "0.7"
 lazy_static = "0.2"
 log = "0.4"
-num = "0.1"
 ordered-float = "0.5"
 time = "0.1"
 petgraph = "0.4.12"
diff --git a/db/src/cache.rs b/db/src/cache.rs
index 144e746d..ef1a7bb4 100644
--- a/db/src/cache.rs
+++ b/db/src/cache.rs
@@ -76,8 +76,6 @@ use failure::{
     ResultExt,
 };
 
-use num;
-
 use rusqlite;
 
 use mentat_core::{
@@ -128,17 +126,10 @@ trait Remove<T> where T: PartialEq {
 
 impl<T> Remove<T> for Vec<T> where T: PartialEq {
     /// Remove all occurrences from a vector in-place, by equality.
-    /// Eventually replace with unstable feature: #40062.
     fn remove_every(&mut self, item: &T) -> usize {
-        let mut removed = 0;
-        let range = num::range_step_inclusive(self.len() as isize - 1, 0, -1);
-        for i in range {
-            if self.get(i as usize).map_or(false, |x| x == item) {
-                self.remove(i as usize);
-                removed += 1;
-            }
-        }
-        removed
+        let initial_len = self.len();
+        self.retain(|v| v != item);
+        initial_len - self.len()
     }
 }
 
@@ -187,10 +178,14 @@ impl<K, V> ExtendByAbsorbing for BTreeMap<K, V> where K: Ord, V: Absorb {
 #[test]
 fn test_vec_remove_item() {
     let mut v = vec![1, 2, 3, 4, 5, 4, 3];
-    v.remove_every(&3);
+    let count = v.remove_every(&3);
     assert_eq!(v, vec![1, 2, 4, 5, 4]);
-    v.remove_every(&4);
+    assert_eq!(count, 2);
+    let count = v.remove_every(&4);
     assert_eq!(v, vec![1, 2, 5]);
+    assert_eq!(count, 2);
+    let count = v.remove_every(&9);
+    assert_eq!(count, 0);
 }
 
 //
diff --git a/db/src/lib.rs b/db/src/lib.rs
index bd8fe154..c42b8eaf 100644
--- a/db/src/lib.rs
+++ b/db/src/lib.rs
@@ -15,7 +15,6 @@ extern crate itertools;
 #[macro_use] extern crate lazy_static;
 #[macro_use] extern crate log;
 
-extern crate num;
 extern crate petgraph;
 extern crate rusqlite;
 extern crate tabwriter;
diff --git a/query-sql/Cargo.toml b/query-sql/Cargo.toml
index 583612e2..72cfaee5 100644
--- a/query-sql/Cargo.toml
+++ b/query-sql/Cargo.toml
@@ -4,7 +4,6 @@ version = "0.0.1"
 workspace = ".."
 
 [dependencies]
-regex = "0.2"
 
 [dependencies.mentat_core]
 path = "../core"
diff --git a/query-sql/src/lib.rs b/query-sql/src/lib.rs
index 47a1655c..32a9ae60 100644
--- a/query-sql/src/lib.rs
+++ b/query-sql/src/lib.rs
@@ -8,7 +8,6 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-extern crate regex;
 #[macro_use] extern crate mentat_core;
 extern crate mentat_query;
 extern crate mentat_query_algebrizer;
@@ -559,15 +558,21 @@ impl QueryFragment for FromClause {
     }
 }
 
+/// `var` is something like `?foo99-people`.
+/// Trim the `?` and escape the rest. Prepend `i` to distinguish from
+/// the inline value space `v`.
+fn format_select_var(var: &str) -> String {
+    use std::iter::once;
+    let without_question = var.split_at(1).1;
+    let replaced_iter = without_question.chars().map(|c|
+        if c.is_ascii_alphanumeric() { c } else { '_' });
+    // Prefix with `i` (Avoiding this copy is probably not worth the trouble but whatever).
+    once('i').chain(replaced_iter).collect()
+}
+
 impl SelectQuery {
     fn push_variable_param(&self, var: &Variable, out: &mut QueryBuilder) -> BuildQueryResult {
-        // `var` is something like `?foo99-people`.
-        // Trim the `?` and escape the rest. Prepend `i` to distinguish from
-        // the inline value space `v`.
-        let re = regex::Regex::new("[^a-zA-Z_0-9]").unwrap();
-        let without_question = var.as_str().split_at(1).1;
-        let replaced = re.replace_all(without_question, "_");
-        let bind_param = format!("i{}", replaced);                 // We _could_ avoid this copying.
+        let bind_param = format_select_var(var.as_str());
         out.push_bind_param(bind_param.as_str())
     }
 }
@@ -817,4 +822,11 @@ mod tests {
         assert!(args.is_empty());
 
     }
+
+    #[test]
+    fn test_format_select_var() {
+        assert_eq!(format_select_var("?foo99-people"), "ifoo99_people");
+        assert_eq!(format_select_var("?FOO99-pëople.123"), "iFOO99_p_ople_123");
+        assert_eq!(format_select_var("?foo①bar越"), "ifoo_bar_");
+    }
 }