From 6e9f95747bb3a12265cfe7e71420a30ec833f907 Mon Sep 17 00:00:00 2001
From: Jefffrey <jeffrey.vo.australia@gmail.com>
Date: Sun, 22 Sep 2024 22:27:38 +1000
Subject: [PATCH] Simplify retrieval of timestamp decoder

---
 src/array_decoder/timestamp.rs | 74 +++++++++++++---------------------
 1 file changed, 29 insertions(+), 45 deletions(-)

diff --git a/src/array_decoder/timestamp.rs b/src/array_decoder/timestamp.rs
index dae7f436..8062719d 100644
--- a/src/array_decoder/timestamp.rs
+++ b/src/array_decoder/timestamp.rs
@@ -44,12 +44,11 @@ const NANOSECOND_DIGITS: i8 = 9;
 /// point for all timestamp values, to the UNIX epoch of 1 January 1970.
 const ORC_EPOCH_UTC_SECONDS_SINCE_UNIX_EPOCH: i64 = 1_420_070_400;
 
-fn get_timestamp_decoder<T: ArrowTimestampType + Send>(
+fn get_inner_timestamp_decoder<T: ArrowTimestampType + Send>(
     column: &Column,
     stripe: &Stripe,
     seconds_since_unix_epoch: i64,
-    is_instant: bool,
-) -> Result<Box<dyn ArrayBatchDecoder>> {
+) -> Result<PrimitiveArrayDecoder<T>> {
     let data = stripe.stream_map().get(column, Kind::Data);
     let data = get_rle_reader(column, data)?;
 
@@ -64,17 +63,31 @@ fn get_timestamp_decoder<T: ArrowTimestampType + Send>(
         data,
         secondary,
     ));
-    let inner = PrimitiveArrayDecoder::<T>::new(iter, present);
-    if is_instant {
-        Ok(Box::new(TimestampInstantArrayDecoder(inner)))
-    } else {
-        match stripe.writer_tz() {
-            Some(writer_tz) => Ok(Box::new(TimestampOffsetArrayDecoder { inner, writer_tz })),
-            None => Ok(Box::new(inner)),
-        }
+    Ok(PrimitiveArrayDecoder::<T>::new(iter, present))
+}
+
+fn get_timestamp_decoder<T: ArrowTimestampType + Send>(
+    column: &Column,
+    stripe: &Stripe,
+    seconds_since_unix_epoch: i64,
+) -> Result<Box<dyn ArrayBatchDecoder>> {
+    let inner = get_inner_timestamp_decoder::<T>(column, stripe, seconds_since_unix_epoch)?;
+    match stripe.writer_tz() {
+        Some(writer_tz) => Ok(Box::new(TimestampOffsetArrayDecoder { inner, writer_tz })),
+        None => Ok(Box::new(inner)),
     }
 }
 
+fn get_timestamp_instant_decoder<T: ArrowTimestampType + Send>(
+    column: &Column,
+    stripe: &Stripe,
+) -> Result<Box<dyn ArrayBatchDecoder>> {
+    // TIMESTAMP_INSTANT is encoded as UTC so we don't check writer timezone in stripe
+    let inner =
+        get_inner_timestamp_decoder::<T>(column, stripe, ORC_EPOCH_UTC_SECONDS_SINCE_UNIX_EPOCH)?;
+    Ok(Box::new(TimestampInstantArrayDecoder(inner)))
+}
+
 fn decimal128_decoder(
     column: &Column,
     stripe: &Stripe,
@@ -151,19 +164,13 @@ pub fn new_timestamp_decoder(
 
     match field_type {
         ArrowDataType::Timestamp(TimeUnit::Second, None) => {
-            get_timestamp_decoder::<TimestampSecondType>(
-                column,
-                stripe,
-                seconds_since_unix_epoch,
-                false,
-            )
+            get_timestamp_decoder::<TimestampSecondType>(column, stripe, seconds_since_unix_epoch)
         }
         ArrowDataType::Timestamp(TimeUnit::Millisecond, None) => {
             get_timestamp_decoder::<TimestampMillisecondType>(
                 column,
                 stripe,
                 seconds_since_unix_epoch,
-                false,
             )
         }
         ArrowDataType::Timestamp(TimeUnit::Microsecond, None) => {
@@ -171,7 +178,6 @@ pub fn new_timestamp_decoder(
                 column,
                 stripe,
                 seconds_since_unix_epoch,
-                false,
             )
         }
         ArrowDataType::Timestamp(TimeUnit::Nanosecond, None) => {
@@ -179,7 +185,6 @@ pub fn new_timestamp_decoder(
                 column,
                 stripe,
                 seconds_since_unix_epoch,
-                false,
             )
         }
         ArrowDataType::Decimal128(Decimal128Type::MAX_PRECISION, NANOSECOND_DIGITS) => {
@@ -206,38 +211,17 @@ pub fn new_timestamp_instant_decoder(
     stripe: &Stripe,
 ) -> Result<Box<dyn ArrayBatchDecoder>> {
     match field_type {
-        // TIMESTAMP_INSTANT is encoded as UTC so we don't check writer timezone in stripe
         ArrowDataType::Timestamp(TimeUnit::Second, Some(tz)) if tz.as_ref() == "UTC" => {
-            get_timestamp_decoder::<TimestampSecondType>(
-                column,
-                stripe,
-                ORC_EPOCH_UTC_SECONDS_SINCE_UNIX_EPOCH,
-                true,
-            )
+            get_timestamp_instant_decoder::<TimestampSecondType>(column, stripe)
         }
         ArrowDataType::Timestamp(TimeUnit::Millisecond, Some(tz)) if tz.as_ref() == "UTC" => {
-            get_timestamp_decoder::<TimestampMillisecondType>(
-                column,
-                stripe,
-                ORC_EPOCH_UTC_SECONDS_SINCE_UNIX_EPOCH,
-                true,
-            )
+            get_timestamp_instant_decoder::<TimestampMillisecondType>(column, stripe)
         }
         ArrowDataType::Timestamp(TimeUnit::Microsecond, Some(tz)) if tz.as_ref() == "UTC" => {
-            get_timestamp_decoder::<TimestampMicrosecondType>(
-                column,
-                stripe,
-                ORC_EPOCH_UTC_SECONDS_SINCE_UNIX_EPOCH,
-                true,
-            )
+            get_timestamp_instant_decoder::<TimestampMicrosecondType>(column, stripe)
         }
         ArrowDataType::Timestamp(TimeUnit::Nanosecond, Some(tz)) if tz.as_ref() == "UTC" => {
-            get_timestamp_decoder::<TimestampNanosecondType>(
-                column,
-                stripe,
-                ORC_EPOCH_UTC_SECONDS_SINCE_UNIX_EPOCH,
-                true,
-            )
+            get_timestamp_instant_decoder::<TimestampNanosecondType>(column, stripe)
         }
         ArrowDataType::Timestamp(_, Some(_)) => UnsupportedTypeVariantSnafu {
             msg: "Non-UTC Arrow timestamps",