style: Histogram -> ColumnMeta

src/execution/volcano/dml/analyze.rs

@@ -17,7 +17,7 @@ use std::sync::Arc;
 use std::time::{SystemTime, UNIX_EPOCH};
 
 const DEFAULT_NUM_OF_BUCKETS: usize = 100;
-const DEFAULT_HISTOGRAM_PATH: &'static str = "kipsql_histograms";
+const DEFAULT_COLUMN_METAS_PATH: &'static str = "kipsql_column_metas";
 
 pub struct Analyze {
     table_name: TableName,
@@ -86,7 +86,7 @@ impl Analyze {
             .as_secs();
         let dir_path = dirs::config_dir()
             .expect("Your system does not have a Config directory!")
-            .join(DEFAULT_HISTOGRAM_PATH)
+            .join(DEFAULT_COLUMN_METAS_PATH)
             .join(table_name.as_str())
             .join(ts.to_string());
         fs::create_dir_all(&dir_path)?;
@@ -108,7 +108,7 @@ impl Analyze {
         transaction.save_table_meta(&meta)?;
 
         let columns: Vec<ColumnRef> = vec![Arc::new(ColumnCatalog::new_dummy(
-            "HISTOGRAM_PATH".to_string(),
+            "COLUMN_META_PATH".to_string(),
         ))];
         let values = meta
             .colum_meta_paths

src/optimizer/core/column_meta.rs

@@ -31,7 +31,7 @@ impl<'a, T: Transaction> ColumnMetaLoader<'a, T> {
         return if let Some(column_metas) = option {
             Ok(column_metas)
         } else {
-            let paths = self.tx.histogram_paths(&table_name)?;
+            let paths = self.tx.column_meta_paths(&table_name)?;
             let mut column_metas = Vec::with_capacity(paths.len());
 
             for path in paths {

src/optimizer/core/histogram.rs

@@ -33,6 +33,7 @@ pub struct Histogram {
     values_len: usize,
 
     buckets: Vec<Bucket>,
+    // TODO: How to use?
     // Correlation is the statistical correlation between physical row ordering and logical ordering of
     // the column values
     correlation: f64,

src/storage/kip.rs

@@ -354,7 +354,7 @@ impl Transaction for KipTransaction {
         Ok(())
     }
 
-    fn histogram_paths(&self, table_name: &str) -> Result<Vec<String>, StorageError> {
+    fn column_meta_paths(&self, table_name: &str) -> Result<Vec<String>, StorageError> {
         if let Some(bytes) = self
             .tx
             .get(&TableCodec::encode_root_table_key(table_name))?

src/storage/mod.rs

@@ -96,7 +96,7 @@ pub trait Transaction: Sync + Send + 'static {
     fn table(&self, table_name: TableName) -> Option<&TableCatalog>;
     fn table_metas(&self) -> Result<Vec<TableMeta>, StorageError>;
     fn save_table_meta(&mut self, table_meta: &TableMeta) -> Result<(), StorageError>;
-    fn histogram_paths(&self, table_name: &str) -> Result<Vec<String>, StorageError>;
+    fn column_meta_paths(&self, table_name: &str) -> Result<Vec<String>, StorageError>;
     fn meta_loader(&self) -> ColumnMetaLoader<Self>
     where
         Self: Sized;