feat: generated columns [WIP]

crates/core/src/delta_datafusion/mod.rs

@@ -81,7 +81,7 @@ use crate::kernel::{Add, DataCheck, EagerSnapshot, Invariant, Snapshot, StructTy
 use crate::logstore::LogStoreRef;
 use crate::table::builder::ensure_table_uri;
 use crate::table::state::DeltaTableState;
-use crate::table::Constraint;
+use crate::table::{Constraint, GeneratedColumn};
 use crate::{open_table, open_table_with_storage_options, DeltaTable};
 
 pub(crate) const PATH_COLUMN: &str = "__delta_rs_path";
@@ -1159,6 +1159,7 @@ pub(crate) async fn execute_plan_to_batch(
 pub struct DeltaDataChecker {
     constraints: Vec<Constraint>,
     invariants: Vec<Invariant>,
+    generated_columns: Vec<GeneratedColumn>,
     non_nullable_columns: Vec<String>,
     ctx: SessionContext,
 }
@@ -1169,6 +1170,7 @@ impl DeltaDataChecker {
         Self {
             invariants: vec![],
             constraints: vec![],
+            generated_columns: vec![],
             non_nullable_columns: vec![],
             ctx: DeltaSessionContext::default().into(),
         }
@@ -1179,6 +1181,7 @@ impl DeltaDataChecker {
         Self {
             invariants,
             constraints: vec![],
+            generated_columns: vec![],
             non_nullable_columns: vec![],
             ctx: DeltaSessionContext::default().into(),
         }
@@ -1189,6 +1192,7 @@ impl DeltaDataChecker {
         Self {
             constraints,
             invariants: vec![],
+            generated_columns: vec![],
             non_nullable_columns: vec![],
             ctx: DeltaSessionContext::default().into(),
         }
@@ -1209,6 +1213,10 @@ impl DeltaDataChecker {
     /// Create a new DeltaDataChecker
     pub fn new(snapshot: &DeltaTableState) -> Self {
         let invariants = snapshot.schema().get_invariants().unwrap_or_default();
+        let generated_columns = snapshot
+            .schema()
+            .get_generated_columns()
+            .unwrap_or_default();
         let constraints = snapshot.table_config().get_constraints();
         let non_nullable_columns = snapshot
             .schema()
@@ -1224,6 +1232,7 @@ impl DeltaDataChecker {
         Self {
             invariants,
             constraints,
+            generated_columns,
             non_nullable_columns,
             ctx: DeltaSessionContext::default().into(),
         }
@@ -1236,7 +1245,9 @@ impl DeltaDataChecker {
     pub async fn check_batch(&self, record_batch: &RecordBatch) -> Result<(), DeltaTableError> {
         self.check_nullability(record_batch)?;
         self.enforce_checks(record_batch, &self.invariants).await?;
-        self.enforce_checks(record_batch, &self.constraints).await
+        self.enforce_checks(record_batch, &self.constraints).await?;
+        self.enforce_checks(record_batch, &self.generated_columns)
+            .await
     }
 
     /// Return true if all the nullability checks are valid

crates/core/src/kernel/error.rs

@@ -65,6 +65,15 @@ pub enum Error {
         line: String,
     },
 
+    /// Error returned when the log contains invalid stats JSON.
+    #[error("Invalid JSON in generation expression, line=`{line}`, err=`{json_err}`")]
+    InvalidGenerationExpressionJson {
+        /// JSON error details returned when parsing the generation expression JSON.
+        json_err: serde_json::error::Error,
+        /// Generation expression.
+        line: String,
+    },
+
     #[error("Table metadata is invalid: {0}")]
     MetadataError(String),
 

crates/core/src/kernel/models/actions.rs

@@ -2,12 +2,14 @@ use std::collections::{HashMap, HashSet};
 use std::fmt::{self, Display};
 use std::str::FromStr;
 
+use delta_kernel::schema::{DataType, StructField};
 use maplit::hashset;
 use serde::{Deserialize, Serialize};
 use tracing::warn;
 use url::Url;
 
 use super::schema::StructType;
+use super::StructTypeExt;
 use crate::kernel::{error::Error, DeltaResult};
 use crate::TableProperty;
 use delta_kernel::table_features::{ReaderFeatures, WriterFeatures};
@@ -115,6 +117,19 @@ impl Metadata {
     }
 }
 
+/// checks if table contains timestamp_ntz in any field including nested fields.
+pub fn contains_timestampntz<'a>(mut fields: impl Iterator<Item = &'a StructField>) -> bool {
+    fn _check_type(dtype: &DataType) -> bool {
+        match dtype {
+            &DataType::TIMESTAMP_NTZ => true,
+            DataType::Array(inner) => _check_type(inner.element_type()),
+            DataType::Struct(inner) => inner.fields().any(|f| _check_type(f.data_type())),
+            _ => false,
+        }
+    }
+    fields.any(|f| _check_type(f.data_type()))
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq, Default)]
 #[serde(rename_all = "camelCase")]
 /// Defines a protocol action
@@ -146,8 +161,8 @@ impl Protocol {
         }
     }
 
-    /// set the reader features in the protocol action, automatically bumps min_reader_version
-    pub fn with_reader_features(
+    /// Append the reader features in the protocol action, automatically bumps min_reader_version
+    pub fn append_reader_features(
         mut self,
         reader_features: impl IntoIterator<Item = impl Into<ReaderFeatures>>,
     ) -> Self {
@@ -156,14 +171,20 @@ impl Protocol {
             .map(Into::into)
             .collect::<HashSet<_>>();
         if !all_reader_features.is_empty() {
-            self.min_reader_version = 3
+            self.min_reader_version = 3;
+            match self.reader_features {
+                Some(mut features) => {
+                    features.extend(all_reader_features);
+                    self.reader_features = Some(features);
+                }
+                None => self.reader_features = Some(all_reader_features),
+            };
         }
-        self.reader_features = Some(all_reader_features);
         self
     }
 
-    /// set the writer features in the protocol action, automatically bumps min_writer_version
-    pub fn with_writer_features(
+    /// Append the writer features in the protocol action, automatically bumps min_writer_version
+    pub fn append_writer_features(
         mut self,
         writer_features: impl IntoIterator<Item = impl Into<WriterFeatures>>,
     ) -> Self {
@@ -172,9 +193,16 @@ impl Protocol {
             .map(|c| c.into())
             .collect::<HashSet<_>>();
         if !all_writer_feautures.is_empty() {
-            self.min_writer_version = 7
+            self.min_writer_version = 7;
+
+            match self.writer_features {
+                Some(mut features) => {
+                    features.extend(all_writer_feautures);
+                    self.writer_features = Some(features);
+                }
+                None => self.writer_features = Some(all_writer_feautures),
+            };
         }
-        self.writer_features = Some(all_writer_feautures);
         self
     }
 
@@ -255,6 +283,32 @@ impl Protocol {
         }
         self
     }
+
+    /// Will apply the column metadata to the protocol by either bumping the version or setting
+    /// features
+    pub fn apply_column_metadata_to_protocol(
+        mut self,
+        schema: &StructType,
+    ) -> DeltaResult<Protocol> {
+        let generated_cols = schema.get_generated_columns()?;
+        let invariants = schema.get_invariants()?;
+        let contains_timestamp_ntz = self.contains_timestampntz(schema.fields());
+
+        if contains_timestamp_ntz {
+            self = self.enable_timestamp_ntz()
+        }
+
+        if !generated_cols.is_empty() {
+            self = self.enable_generated_columns()
+        }
+
+        if !invariants.is_empty() {
+            self = self.enable_invariants()
+        }
+
+        Ok(self)
+    }
+
     /// Will apply the properties to the protocol by either bumping the version or setting
     /// features
     pub fn apply_properties_to_protocol(
@@ -391,10 +445,35 @@ impl Protocol {
         }
         Ok(self)
     }
+
+    /// checks if table contains timestamp_ntz in any field including nested fields.
+    fn contains_timestampntz<'a>(&self, fields: impl Iterator<Item = &'a StructField>) -> bool {
+        contains_timestampntz(fields)
+    }
+
     /// Enable timestamp_ntz in the protocol
-    pub fn enable_timestamp_ntz(mut self) -> Protocol {
-        self = self.with_reader_features(vec![ReaderFeatures::TimestampWithoutTimezone]);
-        self = self.with_writer_features(vec![WriterFeatures::TimestampWithoutTimezone]);
+    fn enable_timestamp_ntz(mut self) -> Self {
+        self = self.append_reader_features([ReaderFeatures::TimestampWithoutTimezone]);
+        self = self.append_writer_features([WriterFeatures::TimestampWithoutTimezone]);
+        self
+    }
+
+    /// Enabled generated columns
+    fn enable_generated_columns(mut self) -> Self {
+        if self.min_writer_version < 4 {
+            self.min_writer_version = 4;
+        }
+        if self.min_writer_version >= 7 {
+            self = self.append_writer_features([WriterFeatures::GeneratedColumns]);
+        }
+        self
+    }
+
+    /// Enabled generated columns
+    fn enable_invariants(mut self) -> Self {
+        if self.min_writer_version >= 7 {
+            self = self.append_writer_features([WriterFeatures::Invariants]);
+        }
         self
     }
 }

crates/core/src/kernel/models/schema.rs

@@ -10,6 +10,7 @@ use serde_json::Value;
 
 use crate::kernel::error::Error;
 use crate::kernel::DataCheck;
+use crate::table::GeneratedColumn;
 
 /// Type alias for a top level schema
 pub type Schema = StructType;
@@ -49,9 +50,39 @@ impl DataCheck for Invariant {
 pub trait StructTypeExt {
     /// Get all invariants in the schemas
     fn get_invariants(&self) -> Result<Vec<Invariant>, Error>;
+
+    /// Get all generated column expressions
+    fn get_generated_columns(&self) -> Result<Vec<GeneratedColumn>, Error>;
 }
 
 impl StructTypeExt for StructType {
+    /// Get all get_generated_columns in the schemas
+    fn get_generated_columns(&self) -> Result<Vec<GeneratedColumn>, Error> {
+        let mut remaining_fields: Vec<(String, StructField)> = self
+            .fields()
+            .map(|field| (field.name.clone(), field.clone()))
+            .collect();
+        let mut generated_cols: Vec<GeneratedColumn> = Vec::new();
+
+        while let Some((field_path, field)) = remaining_fields.pop() {
+            if let Some(MetadataValue::String(generated_col_string)) = field
+                .metadata
+                .get(ColumnMetadataKey::GenerationExpression.as_ref())
+            {
+                let json: Value = serde_json::from_str(generated_col_string).map_err(|e| {
+                    Error::InvalidGenerationExpressionJson {
+                        json_err: e,
+                        line: generated_col_string.to_string(),
+                    }
+                })?;
+                if let Value::String(sql) = json {
+                    generated_cols.push(GeneratedColumn::new(&field_path, &sql, field.data_type()));
+                }
+            }
+        }
+        Ok(generated_cols)
+    }
+
     /// Get all invariants in the schemas
     fn get_invariants(&self) -> Result<Vec<Invariant>, Error> {
         let mut remaining_fields: Vec<(String, StructField)> = self

crates/core/src/operations/add_column.rs

@@ -8,7 +8,7 @@ use itertools::Itertools;
 
 use super::transaction::{CommitBuilder, CommitProperties, PROTOCOL};
 use super::{CustomExecuteHandler, Operation};
-use crate::kernel::StructField;
+use crate::kernel::{StructField, StructTypeExt};
 use crate::logstore::LogStoreRef;
 use crate::operations::cast::merge_schema::merge_delta_struct;
 use crate::protocol::DeltaOperation;
@@ -85,27 +85,26 @@ impl std::future::IntoFuture for AddColumnBuilder {
             this.pre_execute(operation_id).await?;
 
             let fields_right = &StructType::new(fields.clone());
+
+            if !fields_right
+                .get_generated_columns()
+                .unwrap_or_default()
+                .is_empty()
+            {
+                return Err(DeltaTableError::Generic(
+                    "New columns cannot be a generated column".to_string(),
+                ));
+            }
+
             let table_schema = this.snapshot.schema();
             let new_table_schema = merge_delta_struct(table_schema, fields_right)?;
 
-            // TODO(ion): Think of a way how we can simply this checking through the API or centralize some checks.
-            let contains_timestampntz = PROTOCOL.contains_timestampntz(fields.iter());
-            let protocol = this.snapshot.protocol();
-
-            let maybe_new_protocol = if contains_timestampntz {
-                let updated_protocol = protocol.clone().enable_timestamp_ntz();
-                if !(protocol.min_reader_version == 3 && protocol.min_writer_version == 7) {
-                    // Convert existing properties to features since we advanced the protocol to v3,7
-                    Some(
-                        updated_protocol
-                            .move_table_properties_into_features(&metadata.configuration),
-                    )
-                } else {
-                    Some(updated_protocol)
-                }
-            } else {
-                None
-            };
+            let current_protocol = this.snapshot.protocol();
+
+            let new_protocol = current_protocol
+                .clone()
+                .apply_column_metadata_to_protocol(&new_table_schema)?
+                .move_table_properties_into_features(&metadata.configuration);
 
             let operation = DeltaOperation::AddColumn {
                 fields: fields.into_iter().collect_vec(),
@@ -115,7 +114,7 @@ impl std::future::IntoFuture for AddColumnBuilder {
 
             let mut actions = vec![metadata.into()];
 
-            if let Some(new_protocol) = maybe_new_protocol {
+            if current_protocol != &new_protocol {
                 actions.push(new_protocol.into())
             }
 

crates/core/src/operations/add_feature.rs

@@ -123,8 +123,8 @@ impl std::future::IntoFuture for AddTableFeatureBuilder {
                 }
             }
 
-            protocol = protocol.with_reader_features(reader_features);
-            protocol = protocol.with_writer_features(writer_features);
+            protocol = protocol.append_reader_features(reader_features);
+            protocol = protocol.append_writer_features(writer_features);
 
             let operation = DeltaOperation::AddFeature {
                 name: name.to_vec(),

crates/core/src/operations/cdc.rs

@@ -175,7 +175,7 @@ mod tests {
     #[tokio::test]
     async fn test_should_write_cdc_v7_table_with_writer_feature() {
         let protocol =
-            Protocol::new(1, 7).with_writer_features(vec![WriterFeatures::ChangeDataFeed]);
+            Protocol::new(1, 7).append_writer_features(vec![WriterFeatures::ChangeDataFeed]);
         let actions = vec![Action::Protocol(protocol)];
         let mut table: DeltaTable = DeltaOps::new_in_memory()
             .create()