Add test.

tests/queries/0_stateless/01786_explain_merge_tree.reference

@@ -0,0 +1,71 @@
+      ReadFromMergeTree
+      ReadType: Default
+      Indexes:
+        None
+          Parts: 5
+          Granules: 12
+        MinMax
+          Description: unknown, unknown, and, (column 0 in [1, +inf)), unknown, and, unknown, and, and, unknown, unknown, and, and
+          Parts: 4
+          Granules: 11
+        Partition
+          Description: unknown, unknown, and, (column 0 in [1, +inf)), (column 1 not in [1, 1]), and, unknown, and, and, unknown, unknown, and, and
+          Parts: 3
+          Granules: 10
+        PrimaryKey
+          Description: unknown, unknown, and, (column 1 in [1, +inf)), unknown, and, (column 0 in [11, +inf)), and, and, unknown, unknown, and, and
+          Parts: 2
+          Granules: 6
+        Skip
+          Name: t_minmax
+          Description: minmax GRANULARITY 2
+          Parts: 1
+          Granules: 2
+        Skip
+          Name: t_set
+          Description: set GRANULARITY 2
+          Parts: 1
+          Granules: 1
+-----------------
+            ReadFromMergeTree
+            ReadType: InOrder
+            Indexes:
+              None
+                Parts: 5
+                Granules: 12
+              MinMax
+                Description: unknown
+                Parts: 5
+                Granules: 12
+              Partition
+                Description: unknown
+                Parts: 5
+                Granules: 12
+              PrimaryKey
+                Description: (column 0 in [11, +inf))
+                Parts: 2
+                Granules: 6
+            ReadFromMergeTree
+            ReadType: InOrder
+-----------------
+              ReadFromMergeTree
+              ReadType: InReverseOrder
+              Indexes:
+                None
+                  Parts: 5
+                  Granules: 12
+                MinMax
+                  Description: unknown
+                  Parts: 5
+                  Granules: 12
+                Partition
+                  Description: unknown
+                  Parts: 5
+                  Granules: 12
+                PrimaryKey
+                  Description: (column 0 in [11, +inf))
+                  Parts: 2
+                  Granules: 6
+            ReverseRows
+              ReadFromMergeTree
+              ReadType: InReverseOrder

tests/queries/0_stateless/01786_explain_merge_tree.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+
+$CLICKHOUSE_CLIENT -q "create table test_index (x UInt32, y UInt32, z UInt32, t UInt32, index t_minmax t % 20 TYPE minmax GRANULARITY 2, index t_set t % 19 type set(4) granularity 2) engine = MergeTree order by (x, y) partition by (y, bitAnd(z, 3), intDiv(t, 15)) settings index_granularity = 2"
+$CLICKHOUSE_CLIENT -q "insert into test_index select number, number > 3 ? 3 : number, number = 1 ? 1 : 0, number from numbers(20)"
+
+$CLICKHOUSE_CLIENT -q "
+    explain actions = 1 select *, _part from test_index where t % 19 = 16 and y > 0 and bitAnd(z, 3) != 1 and x > 10 and t % 20 > 14;
+    " | grep -A 100 "ReadFromMergeTree"
+
+echo "-----------------"
+
+$CLICKHOUSE_CLIENT -q "
+    explain actions = 1 select x from test_index where x > 10 order by x;
+    " | grep -A 100 "ReadFromMergeTree"
+
+echo "-----------------"
+
+$CLICKHOUSE_CLIENT -q "
+    explain actions = 1 select x from test_index where x > 10 order by x desc;
+    " | grep -A 100 "ReadFromMergeTree"
+