[GitHub] [arrow-rs] tustvold commented on a diff in pull request #3746: Infer 2020-03-19 00:00:00 as timestamp not Date64 in CSV (#3744)

["tustvold (via GitHub)" <gi...@apache.org>]

tustvold commented on code in PR #3746:
URL: https://github.com/apache/arrow-rs/pull/3746#discussion_r1114894599


##########
arrow-csv/src/reader/mod.rs:
##########
@@ -62,44 +61,68 @@ use crate::reader::records::{RecordDecoder, StringRecords};
 use csv::StringRecord;
 
 lazy_static! {
+    /// Order should match [`InferredDataType`]
     static ref REGEX_SET: RegexSet = RegexSet::new([
         r"(?i)^(true)$|^(false)$(?-i)", //BOOLEAN
-        r"^-?((\d*\.\d+|\d+\.\d*)([eE]-?\d+)?|\d+([eE]-?\d+))$", //DECIMAL
         r"^-?(\d+)$", //INTEGER
+        r"^-?((\d*\.\d+|\d+\.\d*)([eE]-?\d+)?|\d+([eE]-?\d+))$", //DECIMAL
         r"^\d{4}-\d\d-\d\d$", //DATE32
-        r"^\d{4}-\d\d-\d\d[T ]\d\d:\d\d:\d\d$", //DATE64
+        r"^\d{4}-\d\d-\d\d[T ]\d\d:\d\d:\d\d$", //Timestamp(Second)
+        r"^\d{4}-\d\d-\d\d[T ]\d\d:\d\d:\d\d.\d{1,3}$", //Timestamp(Millisecond)
+        r"^\d{4}-\d\d-\d\d[T ]\d\d:\d\d:\d\d.\d{1,6}$", //Timestamp(Microsecond)
+        r"^\d{4}-\d\d-\d\d[T ]\d\d:\d\d:\d\d.\d{1,9}$", //Timestamp(Nanosecond)
     ]).unwrap();
-    //The order should match with REGEX_SET
-    static ref MATCH_DATA_TYPE: Vec<DataType> = vec![
-        DataType::Boolean,
-        DataType::Float64,
-        DataType::Int64,
-        DataType::Date32,
-        DataType::Date64,
-    ];
     static ref PARSE_DECIMAL_RE: Regex =
         Regex::new(r"^-?(\d+\.?\d*|\d*\.?\d+)$").unwrap();
-    static ref DATETIME_RE: Regex =
-        Regex::new(r"^\d{4}-\d\d-\d\d[T ]\d\d:\d\d:\d\d\.\d{1,9}$").unwrap();
 }
 
-/// Infer the data type of a record
-fn infer_field_schema(string: &str, datetime_re: Option<Regex>) -> DataType {
-    // when quoting is enabled in the reader, these quotes aren't escaped, we default to
-    // Utf8 for them
-    if string.starts_with('"') {
-        return DataType::Utf8;
-    }
-    let matches = REGEX_SET.matches(string).into_iter().next();
-    // match regex in a particular order
-    match matches {
-        Some(ix) => MATCH_DATA_TYPE[ix].clone(),
-        None => {
-            let datetime_re = datetime_re.unwrap_or_else(|| DATETIME_RE.clone());
-            if datetime_re.is_match(string) {
-                DataType::Timestamp(TimeUnit::Nanosecond, None)
-            } else {
-                DataType::Utf8
+#[derive(Default, Copy, Clone)]
+struct InferredDataType {

Review Comment:
   This logic should be significantly faster as an added bonus



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