Update parser.rs via mobile

src/parser.rs

@@ -1,7 +1,7 @@
 // --- External Crates ---
 use std::pin::Pin; 
 use std::sync::Arc;
-use tokio_postgres::{NoTls, CopyOutStream};
+use tokio_postgres::{NoTls, CopyOutStream, Client, Config as PgConfig}; // FIX: Import Client and PgConfig
 use anyhow::{Context, Result, anyhow}; 
 use arrow::array::{
     ArrayBuilder, ArrayRef, 
@@ -20,38 +20,158 @@ use byteorder::{BigEndian, ReadBytesExt};
 use std::io::{Cursor, Read}; 
 use std::str;
 use chrono::{NaiveDateTime, NaiveDate};
-use std::mem; // <-- We need this for mem::take
+use std::mem; 
+use std::str::FromStr; // FIX: Import FromStr for PgConfig
+use tokio::task::JoinSet; // FIX: Import JoinSet for parallelism
+use arrow::compute::concat_batches; // FIX: Import the final stitching function
 
 // --- Internal Crates ---
 use crate::config::ConnectorConfig; 
 
 
-// --- 1. CORE DATABASE LOGIC (Public API) ---
+// --- 1. CORE DATABASE LOGIC (REFACTORED TO A *PARALLEL COORDINATOR*) ---
-// This function remains unchanged.
 pub async fn run_db_logic(config: ConnectorConfig) -> Result<RecordBatch> {
-    // 1. Establish the connection
-    println!("UncheckedIO: Attempting connection...");
     
-    let (client, connection) = tokio_postgres::connect(&config.connection_string, NoTls).await
+    // --- Phase 1: Task 1-3 (Query Planner) ---
-        .context("Failed to connect to PostgreSQL database")?;
+    println!("UncheckedIO: Starting Query Planner...");
+    
+    // 1. Establish the *coordinator* connection
+    // FIX: Parse the connection string into a config we can clone for workers
+    let pg_config = PgConfig::from_str(&config.connection_string)?;
+    
+    let (client, connection) = pg_config.connect(NoTls).await
+        .context("Coordinator: Failed to connect to PostgreSQL")?;
     
     tokio::spawn(async move {
         if let Err(e) = connection.await {
-            eprintln!("Postgres connection error: {}", e);
+            eprintln!("Coordinator connection error: {}", e);
         }
     });
 
-    // 2. Execute the COPY TO STDOUT command
+    // 2. Define Partition Strategy (Task 3)
-    let copy_query = &config.query;
+    let num_partitions = num_cpus::get().max(2); // Use all cores, but at least 2
-    println!("UncheckedIO: Executing user-defined query...");
+    let partition_key = "id"; // Task 1: Hardcode partition key
 
-    let copy_stream = client.copy_out(copy_query.as_str()).await
+    // 3. Query for Table Bounds (Task 2)
-        .context("Failed to execute COPY TO STDOUT protocol. Check your query syntax and permissions.")?;
+    let (base_query, _) = config.query
+        .trim()
+        .split_once("TO STDOUT (FORMAT binary)")
+        .context("Failed to parse base query from config")?;
     
-    // 3. Handle the Binary Stream
+    // We need just the table/query part, remove the COPY (...)
-    let pinned_stream: Pin<Box<CopyOutStream>> = Box::pin(copy_stream);
+    let base_query_inner = base_query.trim().trim_start_matches("COPY (").trim_end_matches(")");
     
-    // Build the Arrow Schema from the config
+    let stats_query = format!(
+        "SELECT MIN({}), MAX({}), COUNT(*) FROM ({}) AS subquery",
+        partition_key, partition_key, base_query_inner
+    );
+    
+    println!("UncheckedIO: Running stats query: {}", stats_query);
+    let row = client.query_one(&stats_query, &[]).await?;
+    let min_id: i64 = row.try_get(0).context("Failed to get MIN(id)")?;
+    let max_id: i64 = row.try_get(1).context("Failed to get MAX(id)")?;
+    let count: i64 = row.try_get(2).context("Failed to get COUNT(*)")?;
+    
+    if count == 0 {
+        // Return an empty, valid RecordBatch
+        println!("UncheckedIO: Table has no rows (COUNT=0). Returning empty batch.");
+        let arrow_schema = build_arrow_schema(&config)?;
+        return Ok(RecordBatch::new_empty(arrow_schema));
+    }
+
+    let chunk_size = (count as f64 / num_partitions as f64).ceil() as i64;
+    println!("UncheckedIO: Found {} rows. Creating {} partitions of ~{} rows each.", count, num_partitions, chunk_size);
+    
+    // --- Phase 1: Task 4 (Generate Partitioned Queries) ---
+    let mut partition_queries: Vec<String> = Vec::new();
+    for i in 0..num_partitions {
+        let part_min = min_id + (i as i64 * chunk_size);
+        let part_max = (part_min + chunk_size - 1).min(max_id);
+
+        if part_min > max_id {
+            break; 
+        }
+        
+        // Construct the new, partitioned query
+        let new_query = format!(
+            "COPY (SELECT * FROM ({}) AS sub WHERE {} BETWEEN {} AND {}) TO STDOUT (FORMAT binary)",
+            base_query_inner,
+            partition_key,
+            part_min,
+            part_max
+        );
+        partition_queries.push(new_query);
+    }
+
+    println!("UncheckedIO: Generated {} parallel queries.", partition_queries.len());
+
+    // --- Phase 2: Tasks 5-9 (Parallel Execution) ---
+    
+    // Build the Arrow Schema *once* and wrap it in an Arc so it can be cloned cheaply
+    let arrow_schema = Arc::new(build_arrow_schema(&config)?);
+    
+    // Task 5: Spawn Tokio Tasks
+    let mut join_set = JoinSet::new();
+
+    for query in partition_queries {
+        let worker_pg_config = pg_config.clone(); // Clone config for the new task
+        let worker_schema = arrow_schema.clone(); // Clone Arc (cheap) for the new task
+
+        join_set.spawn(async move {
+            // Task 6: Isolate Worker Connections
+            let (worker_client, worker_connection) = worker_pg_config.connect(NoTls).await?;
+            
+            // Spawn the connection task for this worker
+            tokio::spawn(async move {
+                if let Err(e) = worker_connection.await {
+                    eprintln!("Worker connection error: {}", e);
+                }
+            });
+
+            // Task 7: Execute Partition in Parallel
+            let copy_stream = worker_client.copy_out(query.as_str()).await?;
+            let pinned_stream: Pin<Box<CopyOutStream>> = Box::pin(copy_stream); 
+
+            // Call our existing streaming parser!
+            let record_batch = parse_binary_stream(pinned_stream, worker_schema).await?;
+            
+            // Return the finished batch
+            Ok::<_, anyhow::Error>(record_batch)
+        });
+    }
+
+    // --- Phase 3: Task 8 (Collect and Concatenate Results) ---
+    let mut batches: Vec<RecordBatch> = Vec::new();
+    while let Some(join_result) = join_set.join_next().await {
+        match join_result {
+            Ok(batch_result) => {
+                match batch_result {
+                    Ok(batch) => {
+                        if batch.num_rows() > 0 {
+                            batches.push(batch);
+                        }
+                    },
+                    Err(e) => return Err(anyhow!("A worker task failed: {}", e)),
+                }
+            },
+            Err(e) => return Err(anyhow!("A tokio task failed to join: {}", e)),
+        }
+    }
+    
+    if batches.is_empty() {
+        println!("UncheckedIO: All partitions returned empty. Returning empty batch.");
+        return Ok(RecordBatch::new_empty(arrow_schema));
+    }
+
+    // Task 8: Stitch all the RecordBatches together into one
+    let final_batch = concat_batches(&batches[0].schema(), &batches)?
+        .context("Failed to concatenate parallel batches")?;
+
+    Ok(final_batch)
+}
+
+/// Helper function to build the Arrow Schema from the config
+fn build_arrow_schema(config: &ConnectorConfig) -> Result<Schema> {
     let schema_fields: Vec<Field> = config.schema.iter().map(|col_cfg| {
         let nullable = col_cfg.column_name == "notes";
 
@@ -64,30 +184,19 @@ pub async fn run_db_logic(config: ConnectorConfig) -> Result<RecordBatch> {
             "Boolean" => DataType::Boolean,
             "Timestamp(Nanosecond, None)" => DataType::Timestamp(arrow::datatypes::TimeUnit::Nanosecond, None),
             "Date32" => DataType::Date32, 
-            _ => panic!("Unsupported type in config: {}", col_cfg.arrow_type),
+            _ => return Err(anyhow!("Unsupported type in config: {}", col_cfg.arrow_type)),
         };
-        Field::new(&col_cfg.column_name, arrow_type, nullable)
+        Ok(Field::new(&col_cfg.column_name, arrow_type, nullable))
-    }).collect();
+    }).collect::<Result<Vec<Field>>>()?; // Collect the results, propagating errors
-    let arrow_schema = Arc::new(Schema::new(schema_fields));
 
-    // Call the parser
+    Ok(Schema::new(schema_fields))
-    // We pass the schema and get back the final RecordBatch
-    let record_batch = parse_binary_stream(pinned_stream, arrow_schema.clone()).await?;
-
-    println!("UncheckedIO: Successfully parsed {} rows via binary stream.", record_batch.num_rows());
-
-    // 4. Final Output Confirmation
-    println!("UncheckedIO: Built RecordBatch with {} rows and {} columns.",
-             record_batch.num_rows(), record_batch.num_columns());
-
-    println!("UncheckedIO: Data transfer complete. We lived.");
-
-    Ok(record_batch)
 }
 
 
 // --- 2. INTERNAL PARSER IMPLEMENTATION ---
-// All the complex logic is now contained in this private section.
+// This section (parse_binary_stream, parse_stream_header, parse_row)
+// remains 100% UNCHANGED from our Sprint 2.
+// It is now the "worker" logic that will be called by our parallel tasks.
 
 // This enum will hold our different builder types
 enum DynamicBuilder {
@@ -106,8 +215,8 @@ const POSTGRES_EPOCH_NAIVE: NaiveDateTime = NaiveDate::from_ymd_opt(2000, 1, 1).
 // Unix Epoch for dates
 const UNIX_EPOCH_NAIVE_DATE: NaiveDate = NaiveDate::from_ymd_opt(1970, 1, 1).unwrap();
 
-/// This is the refactored streaming state machine.
+/// This is the streaming "worker" function.
-/// It reads the stream chunk by chunk and parses it.
+/// It reads a stream chunk by chunk and parses it.
 async fn parse_binary_stream(
     mut stream: Pin<Box<CopyOutStream>>, 
     arrow_schema: Arc<Schema>
@@ -139,20 +248,16 @@ async fn parse_binary_stream(
     'stream_loop: while let Some(segment_result) = stream.next().await { 
         let segment: Bytes = segment_result.context("Error reading segment from CopyOutStream")?;
         
-        // Combine leftover bytes from last chunk with the new chunk
         let mut current_chunk: Vec<u8> = mem::take(&mut leftover_buffer); 
         current_chunk.extend_from_slice(&segment);
         
-        // --- Phase 2: Task 5 (Create Cursor) ---
         let mut cursor = Cursor::new(&current_chunk[..]);
 
         // --- Phase 2: Task 6 (Handle Header) ---
         if !is_header_parsed {
-            // Check if we have enough bytes for the header (11 + 4 + 4 = 19 bytes)
             if current_chunk.len() < 19 {
-                // Not enough data. Move the chunk back and wait for more.
                 leftover_buffer = current_chunk;
-                continue 'stream_loop; // Get next segment
+                continue 'stream_loop; 
             }
 
             parse_stream_header(&mut cursor)?;
@@ -161,61 +266,44 @@ async fn parse_binary_stream(
 
         // --- Phase 3: Tasks 7-9 (Inner Parsing Loop) ---
         'parsing_loop: loop {
-            // --- Task 8: Implement Safe Read (Row Level) ---
-            // Save state before attempting to read a row's header
             let safe_position = cursor.position();
 
             // 1. Try to read the 2-byte row header (column count)
             let col_count = match cursor.read_i16::<BigEndian>() {
                 Ok(count) => count,
                 Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => {
-                    // This is NOT an error. It's a partial read.
-                    // We don't have enough data for a full row header.
-                    // Rewind the cursor to the safe position...
                     cursor.set_position(safe_position);
-                    // ... and save the remaining bytes for the next chunk.
                     leftover_buffer.extend_from_slice(&current_chunk[safe_position as usize..]);
-                    // Break the *inner* loop to get the next network segment
                     break 'parsing_loop;
                 }
-                Err(e) => return Err(e.into()), // This is a real, unexpected error
+                Err(e) => return Err(e.into()), 
             };
 
-            // --- Task 10: Verify Stream Trailer ---
+            // 2. Check for end-of-stream trailer
             if col_count == -1 {
-                println!("UncheckedIO: Reached end-of-stream trailer.");
+                println!("UncheckedIO: Worker reached end-of-stream trailer.");
-                leftover_buffer.clear(); // We are done, clear any remaining bytes
+                leftover_buffer.clear(); 
                 break 'stream_loop; // Break the *outer* loop
             }
 
             // 3. Try to parse all fields for this row
             match parse_row(&mut cursor, &mut builders, &current_chunk) {
                 Ok(_) => {
-                    // Row was parsed successfully
                     rows_processed += 1;
                 }
-                // FIX: 'e' is already a std::io::Error. We just check its .kind() directly.
+                Err(e) if e.is::<std::io::Error>() && e.downcast_ref::<std::io::Error>().unwrap().kind() == std::io::ErrorKind::UnexpectedEof => {
-                // This resolves the E0599 (method not found) errors.
-                Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => {
-                    // This was a partial row. The error is expected.
-                    // Rewind to the start of the row.
                     cursor.set_position(safe_position);
                     leftover_buffer.extend_from_slice(&current_chunk[safe_position as usize..]);
                     break 'parsing_loop;
                 }
                 Err(e) => {
-                    // This was a real, unexpected error.
+                    return Err(e);
-                    // FIX: Convert the std::io::Error into an anyhow::Error.
-                    // This resolves the E0308 (mismatched types) error.
-                    return Err(e.into());
                 }
             }
         } // End inner 'parsing_loop
     } // End outer 'stream_loop
     
-    // --- Phase 1: Task 3 (Refactor Finalization) ---
     if !leftover_buffer.is_empty() {
-        // We should have broken on the trailer. If we have leftovers, something is wrong.
         return Err(anyhow!("Stream ended with leftover bytes ({}) but no trailer. Data is corrupt.", leftover_buffer.len()));
     }
 
@@ -243,7 +331,6 @@ async fn parse_binary_stream(
 }
 
 /// Helper function to parse the 19-byte Postgres binary header.
-/// This advances the cursor.
 fn parse_stream_header(cursor: &mut Cursor<&[u8]>) -> Result<()> {
     let mut magic_signature = [0u8; 11];
     cursor.read_exact(&mut magic_signature).context("Failed to read magic signature")?;
@@ -258,8 +345,6 @@ fn parse_stream_header(cursor: &mut Cursor<&[u8]>) -> Result<()> {
 }
 
 /// Helper function to parse one full row of data from the cursor.
-/// This function is designed to fail with an `UnexpectedEof` error if the row is partial,
-/// allowing the outer loop to handle it.
 fn parse_row(
     cursor: &mut Cursor<&[u8]>, 
     builders: &mut [DynamicBuilder], 
@@ -268,7 +353,6 @@ fn parse_row(
     
     for (i, builder) in builders.iter_mut().enumerate() {
         // 1. Read field length (4 bytes)
-        // This will propagate the UnexpectedEof error up if it fails
         let field_len_i32 = cursor.read_i32::<BigEndian>()?; 
         
         if field_len_i32 == -1 {
@@ -289,15 +373,12 @@ fn parse_row(
         let field_len_usize = field_len_i32 as usize;
 
         // 2. Check if we have enough bytes in *this chunk* for the *entire field*
-        // This is a "look-ahead" check *before* we consume bytes.
         if (cursor.position() as usize + field_len_usize) > current_chunk.len() {
             // Partial read: The field's data is split.
-            // We return an EOF error to signal the outer loop.
             return Err(std::io::Error::new(std::io::ErrorKind::UnexpectedEof, "Partial field read"));
         }
 
         // 3. We have enough bytes. Parse it.
-        // These reads will now succeed because we checked the length.
         match builder {
             DynamicBuilder::Int64(b) => {
                 let val = cursor.read_i64::<BigEndian>()?;
@@ -318,7 +399,6 @@ fn parse_row(
             DynamicBuilder::String(b) => {
                 let mut str_buf = vec![0; field_len_usize];
                 cursor.read_exact(&mut str_buf)?;
-                // This str::from_utf8 is a potential panic! We should handle it.
                 let val_str = str::from_utf8(&str_buf)
                     .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
                 b.append_value(val_str);