fix: return MergeIterator.Close errors (#24975) (#24997)

Ensure that errors from closing the
iterators underneath a MergeIterator
are returned up the stack.

(cherry picked from commit 5fda409f39)

closes https://github.com/influxdata/influxdb/issues/24977

influxql/query/iterator.gen.go

@@ -10,6 +10,7 @@ package query
 import (
 	"container/heap"
 	"context"
+	"errors"
 	"io"
 	"sort"
 	"sync"
@@ -162,14 +163,15 @@ func (itr *floatMergeIterator) Close() error {
 	itr.mu.Lock()
 	defer itr.mu.Unlock()
 
+	var errs []error
 	for _, input := range itr.inputs {
-		input.Close()
+		errs = append(errs, input.Close())
 	}
 	itr.curr = nil
 	itr.inputs = nil
 	itr.heap.items = nil
 	itr.closed = true
-	return nil
+	return errors.Join(errs...)
 }
 
 // Next returns the next point from the iterator.
@@ -2825,14 +2827,15 @@ func (itr *integerMergeIterator) Close() error {
 	itr.mu.Lock()
 	defer itr.mu.Unlock()
 
+	var errs []error
 	for _, input := range itr.inputs {
-		input.Close()
+		errs = append(errs, input.Close())
 	}
 	itr.curr = nil
 	itr.inputs = nil
 	itr.heap.items = nil
 	itr.closed = true
-	return nil
+	return errors.Join(errs...)
 }
 
 // Next returns the next point from the iterator.
@@ -5488,14 +5491,15 @@ func (itr *unsignedMergeIterator) Close() error {
 	itr.mu.Lock()
 	defer itr.mu.Unlock()
 
+	var errs []error
 	for _, input := range itr.inputs {
-		input.Close()
+		errs = append(errs, input.Close())
 	}
 	itr.curr = nil
 	itr.inputs = nil
 	itr.heap.items = nil
 	itr.closed = true
-	return nil
+	return errors.Join(errs...)
 }
 
 // Next returns the next point from the iterator.
@@ -8151,14 +8155,15 @@ func (itr *stringMergeIterator) Close() error {
 	itr.mu.Lock()
 	defer itr.mu.Unlock()
 
+	var errs []error
 	for _, input := range itr.inputs {
-		input.Close()
+		errs = append(errs, input.Close())
 	}
 	itr.curr = nil
 	itr.inputs = nil
 	itr.heap.items = nil
 	itr.closed = true
-	return nil
+	return errors.Join(errs...)
 }
 
 // Next returns the next point from the iterator.
@@ -10800,14 +10805,15 @@ func (itr *booleanMergeIterator) Close() error {
 	itr.mu.Lock()
 	defer itr.mu.Unlock()
 
+	var errs []error
 	for _, input := range itr.inputs {
-		input.Close()
+		errs = append(errs, input.Close())
 	}
 	itr.curr = nil
 	itr.inputs = nil
 	itr.heap.items = nil
 	itr.closed = true
-	return nil
+	return errors.Join(errs...)
 }
 
 // Next returns the next point from the iterator.

influxql/query/iterator.gen.go.tmpl

@@ -4,6 +4,7 @@ package query
 import (
 	"context"
 	"container/heap"
+	"errors"
 	"io"
 	"sort"
 	"sync"
@@ -159,14 +160,15 @@ func (itr *{{$k.name}}MergeIterator) Close() error {
 	itr.mu.Lock()
 	defer itr.mu.Unlock()
 
+    var errs []error
 	for _, input := range itr.inputs {
-		input.Close()
+		errs = append(errs, input.Close())
 	}
 	itr.curr = nil
 	itr.inputs = nil
 	itr.heap.items = nil
 	itr.closed = true
-	return nil
+	return errors.Join(errs...)
 }
 
 // Next returns the next point from the iterator.