fix: wrong calc of #rows of page in http handler. (#17839)

Author: youngsofun

src/query/service/src/servers/http/v1/query/page_manager.rs

@@ -134,6 +134,7 @@ impl PageManager {
         remain_rows: &mut usize,
         remain_size: &mut usize,
     ) -> Result<()> {
+        assert!(self.row_buffer.is_none());
         if block.is_empty() {
             return Ok(());
         }
@@ -148,10 +149,11 @@ impl PageManager {
             .map(|entry| entry.to_column(block.num_rows()))
             .collect_vec();
 
+        let block_memory_size = block.memory_size();
         let mut take_rows = min(
             *remain_rows,
-            if block.memory_size() > *remain_size {
-                (*remain_size * block.num_rows()) / block.memory_size()
+            if block_memory_size > *remain_size {
+                (*remain_size * block.num_rows()) / block_memory_size
             } else {
                 block.num_rows()
             },
@@ -161,17 +163,15 @@ impl PageManager {
             take_rows = 1;
         }
 
-        // theoretically, it should always be smaller than the memory_size of the block.
-        *remain_size -= min(
-            *remain_size,
-            take_rows * block.memory_size() / block.num_rows(),
-        );
-        *remain_rows -= take_rows;
-
         if take_rows == block.num_rows() {
+            // theoretically, it should always be smaller than the memory_size of the block.
+            *remain_size -= min(*remain_size, block_memory_size);
+            *remain_rows -= take_rows;
             serializer.append(columns, block.num_rows());
-            self.row_buffer = None;
         } else {
+            // Since not all rows of the block are used, either the size limit or the row limit must have been exceeded.
+            // simply set any of remain_xxx to end the page.
+            *remain_rows = 0;
             let fn_slice = |columns: &[Column], range: Range<usize>| {
                 columns
                     .iter()

tests/suites/1_stateful/09_http_handler/09_0004_large_row.result

@@ -1,3 +1,4 @@
 1
 1
 0
+100000

tests/suites/1_stateful/09_http_handler/09_0004_large_row.sh

@@ -16,3 +16,7 @@ curl -s --header 'Content-Type: application/json'  "127.0.0.1:8000/v1/query/$qid
 
 curl -s --header 'Content-Type: application/json'  "127.0.0.1:8000/v1/query/$qid/page/2" \
  -u root: | jq '.data | length'
+
+# rows have diff sizes
+# row size >  (max_size / max_rows) = 10M / 10000
+echo "SELECT  repeat(number::string, 2000)  from numbers(100000)" |  $BENDSQL_CLIENT_CONNECT  | wc -l | sed 's/ //g'