fix examples so that they all work with scylla

Author: wmitros

README.md

@@ -40,11 +40,11 @@ wasm2wat target/wasm32-wasi/debug/abc.wasm > target/wasm32/wasi/debug/abc.wat
 ### CQL Statement
 
 The resulting `target/wasm32/wasi/debug/abc.wat` code can now be used directly in a `CREATE FUNCTION` statement. The resulting code will most likely
-contain `'` characters, so it's recommended to use a `LANGUAGE xwasm AS $$ (module ...) $$` clause instead of `LANGUAGE xwasm AS ' (module ...) '`.
+contain `'` characters, so it may be necessary to first replace them with `''`, so that they're usable in a CQL string.
 
-For example, if you have an [Rust UDF](examples/commas.rs) that joins a list of words using commas you can create a Scylla UDF using the following statement:
+For example, if you have an [Rust UDF](examples/commas.rs) that joins a list of words using commas, you can create a Scylla UDF using the following statement:
 ```
-CREATE FUNCTION commas(string list<text>) CALLED ON NULL INPUT RETURNS text AS $$ (module ...) $$
+CREATE FUNCTION commas(string list<text>) CALLED ON NULL INPUT RETURNS text AS ' (module ...) '
 ```
 
 

examples/combine.rs

@@ -1,11 +1,10 @@
-use scylla_udf::{export_udf, Counter, CqlDuration, Time, Timestamp};
+use scylla_udf::{export_udf, CqlDuration, Time, Timestamp};
 
 #[allow(clippy::too_many_arguments, clippy::type_complexity)]
 #[export_udf]
 fn combine(
     b: bool,
     blob: Vec<u8>,
-    cnt: Counter,
     date: chrono::NaiveDate,
     bd: bigdecimal::BigDecimal,
     dbl: f64,
@@ -25,7 +24,6 @@ fn combine(
     (
         bool,
         Vec<u8>,
-        Counter,
         chrono::NaiveDate,
         bigdecimal::BigDecimal,
         f64,
@@ -46,7 +44,7 @@ fn combine(
     ),
 ) {
     (
-        (b, blob, cnt, date, bd, dbl, cqldur, flt, int32, int64),
+        (b, blob, date, bd, dbl, cqldur, flt, int32, int64),
         (s, tstamp, ip, int16, int8, tim, uid, bi),
     )
 }

examples/topn.rs

@@ -6,33 +6,45 @@ struct StringLen(String);
 
 impl std::cmp::PartialEq for StringLen {
     fn eq(&self, other: &Self) -> bool {
-        self.0.len() == other.0.len()
+        self.0 == other.0
     }
 }
 
 impl std::cmp::Eq for StringLen {}
 
 impl std::cmp::PartialOrd for StringLen {
     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        Some(self.0.len().cmp(&other.0.len()))
+        Some(self.cmp(other))
     }
 }
 
 impl std::cmp::Ord for StringLen {
     fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        self.0.len().cmp(&other.0.len())
+        if self.0.len().cmp(&other.0.len()) == std::cmp::Ordering::Equal {
+            self.0.cmp(&other.0)
+        } else {
+            self.0.len().cmp(&other.0.len())
+        }
     }
 }
 
 // Store the top N strings by length, without repetitions.
 #[export_udf]
-fn topn_row((n, mut acc): (i32, BTreeSet<StringLen>), v: StringLen) -> (i32, BTreeSet<StringLen>) {
-    acc.insert(v);
-    while acc.len() > n as usize {
-        acc.pop_first();
+fn topn_row(
+    acc_tup: Option<(i32, BTreeSet<StringLen>)>,
+    v: Option<StringLen>,
+) -> Option<(i32, BTreeSet<StringLen>)> {
+    if let Some((n, mut acc)) = acc_tup {
+        if let Some(v) = v {
+            acc.insert(v);
+            while acc.len() > n as usize {
+                acc.pop_first();
+            }
+        }
+        Some((n, acc))
+    } else {
+        None
     }
-
-    (n, acc)
 }
 
 #[export_udf]