Add COMMENT support to CREATE VIEW parser (#265)

sharadgaur · web-flow · commit 8ce1476f64ea · 2026-04-17T23:15:09.000+08:00
CREATE VIEW in ClickHouse supports COMMENT between the schema and AS SELECT:

  CREATE VIEW db.v (columns) COMMENT '{...}' AS SELECT ...

The parser previously failed with 'expected EOF or ; but got COMMENT'.

Changes:
- Add Comment field to CreateView struct (ast.go)
- Parse COMMENT clause in parseCreateView before AS (parser_view.go)
- Format COMMENT in CreateView.FormatSQL (format.go)
- Add test case: create_view_with_comment.sql
- Update golden files for existing view tests (new nil Comment field)
diff --git a/parser/ast.go b/parser/ast.go
@@ -1452,6 +1452,7 @@ type CreateView struct {
 	UUID         *UUID
 	OnCluster    *ClusterClause
 	TableSchema  *TableSchemaClause
+	Comment      *StringLiteral
 	SubQuery     *SubQuery
 }
 
@@ -1488,6 +1489,11 @@ func (c *CreateView) Accept(visitor ASTVisitor) error {
 			return err
 		}
 	}
+	if c.Comment != nil {
+		if err := c.Comment.Accept(visitor); err != nil {
+			return err
+		}
+	}
 	if c.SubQuery != nil {
 		if err := c.SubQuery.Accept(visitor); err != nil {
 			return err
diff --git a/parser/format.go b/parser/format.go
@@ -1139,6 +1139,11 @@ func (c *CreateView) FormatSQL(formatter *Formatter) {
 		formatter.WriteExpr(c.TableSchema)
 	}
 
+	if c.Comment != nil {
+		formatter.WriteString(" COMMENT ")
+		formatter.WriteExpr(c.Comment)
+	}
+
 	if c.SubQuery != nil {
 		formatter.WriteString(" AS ")
 		formatter.WriteExpr(c.SubQuery)
diff --git a/parser/parser_view.go b/parser/parser_view.go
@@ -240,6 +240,13 @@ func (p *Parser) parseCreateView(pos Pos, orReplace bool) (*CreateView, error) {
 		createView.TableSchema = tableSchema
 	}
 
+	// parse COMMENT clause if exists (before AS SELECT)
+	comment, err := p.tryParseComment()
+	if err != nil {
+		return nil, err
+	}
+	createView.Comment = comment
+
 	if p.tryConsumeKeywords(KeywordAs) {
 		subQuery, err := p.parseSubQuery(p.Pos())
 		if err != nil {
diff --git a/parser/testdata/ddl/create_view_with_comment.sql b/parser/testdata/ddl/create_view_with_comment.sql
@@ -0,0 +1,10 @@
+CREATE VIEW IF NOT EXISTS db.my_view
+(
+    `id` Int64,
+    `name` String
+)
+COMMENT '{"blueprint_hash":"abc123"}'
+AS SELECT
+    id,
+    name
+FROM db.my_table;
diff --git a/parser/testdata/ddl/format/beautify/create_view_with_comment.sql b/parser/testdata/ddl/format/beautify/create_view_with_comment.sql
@@ -0,0 +1,22 @@
+-- Origin SQL:
+CREATE VIEW IF NOT EXISTS db.my_view
+(
+    `id` Int64,
+    `name` String
+)
+COMMENT '{"blueprint_hash":"abc123"}'
+AS SELECT
+    id,
+    name
+FROM db.my_table;
+
+
+-- Beautify SQL:
+CREATE VIEW IF NOT EXISTS db.my_view (
+  `id` Int64,
+  `name` String
+) COMMENT '{"blueprint_hash":"abc123"}' AS SELECT
+  id,
+  name
+FROM
+  db.my_table;
diff --git a/parser/testdata/ddl/format/create_view_with_comment.sql b/parser/testdata/ddl/format/create_view_with_comment.sql
@@ -0,0 +1,15 @@
+-- Origin SQL:
+CREATE VIEW IF NOT EXISTS db.my_view
+(
+    `id` Int64,
+    `name` String
+)
+COMMENT '{"blueprint_hash":"abc123"}'
+AS SELECT
+    id,
+    name
+FROM db.my_table;
+
+
+-- Format SQL:
+CREATE VIEW IF NOT EXISTS db.my_view (`id` Int64, `name` String) COMMENT '{"blueprint_hash":"abc123"}' AS SELECT id, name FROM db.my_table;
diff --git a/parser/testdata/ddl/output/create_or_replace.sql.golden.json b/parser/testdata/ddl/output/create_or_replace.sql.golden.json
@@ -409,6 +409,7 @@
       "AliasTable": null,
       "TableFunction": null
     },
+    "Comment": null,
     "SubQuery": {
       "HasParen": false,
       "Select": {
diff --git a/parser/testdata/ddl/output/create_view_basic.sql.golden.json b/parser/testdata/ddl/output/create_view_basic.sql.golden.json
@@ -83,6 +83,7 @@
       "AliasTable": null,
       "TableFunction": null
     },
+    "Comment": null,
     "SubQuery": {
       "HasParen": false,
       "Select": {
diff --git a/parser/testdata/ddl/output/create_view_on_cluster_with_uuid.sql.golden.json b/parser/testdata/ddl/output/create_view_on_cluster_with_uuid.sql.golden.json
@@ -34,6 +34,7 @@
       }
     },
     "TableSchema": null,
+    "Comment": null,
     "SubQuery": {
       "HasParen": true,
       "Select": {
diff --git a/parser/testdata/ddl/output/create_view_with_comment.sql.golden.json b/parser/testdata/ddl/output/create_view_with_comment.sql.golden.json
@@ -0,0 +1,172 @@
+[
+  {
+    "CreatePos": 0,
+    "StatementEnd": 156,
+    "OrReplace": false,
+    "Name": {
+      "Database": {
+        "Name": "db",
+        "QuoteType": 1,
+        "NamePos": 26,
+        "NameEnd": 28
+      },
+      "Table": {
+        "Name": "my_view",
+        "QuoteType": 1,
+        "NamePos": 29,
+        "NameEnd": 36
+      }
+    },
+    "IfNotExists": true,
+    "UUID": null,
+    "OnCluster": null,
+    "TableSchema": {
+      "SchemaPos": 37,
+      "SchemaEnd": 73,
+      "Columns": [
+        {
+          "NamePos": 44,
+          "ColumnEnd": 53,
+          "Name": {
+            "Ident": {
+              "Name": "id",
+              "QuoteType": 3,
+              "NamePos": 44,
+              "NameEnd": 46
+            },
+            "DotIdent": null
+          },
+          "Type": {
+            "Name": {
+              "Name": "Int64",
+              "QuoteType": 1,
+              "NamePos": 48,
+              "NameEnd": 53
+            }
+          },
+          "NotNull": null,
+          "Nullable": null,
+          "DefaultExpr": null,
+          "MaterializedExpr": null,
+          "AliasExpr": null,
+          "Codec": null,
+          "TTL": null,
+          "Comment": null,
+          "CompressionCodec": null
+        },
+        {
+          "NamePos": 60,
+          "ColumnEnd": 72,
+          "Name": {
+            "Ident": {
+              "Name": "name",
+              "QuoteType": 3,
+              "NamePos": 60,
+              "NameEnd": 64
+            },
+            "DotIdent": null
+          },
+          "Type": {
+            "Name": {
+              "Name": "String",
+              "QuoteType": 1,
+              "NamePos": 66,
+              "NameEnd": 72
+            }
+          },
+          "NotNull": null,
+          "Nullable": null,
+          "DefaultExpr": null,
+          "MaterializedExpr": null,
+          "AliasExpr": null,
+          "Codec": null,
+          "TTL": null,
+          "Comment": null,
+          "CompressionCodec": null
+        }
+      ],
+      "AliasTable": null,
+      "TableFunction": null
+    },
+    "Comment": {
+      "LiteralPos": 84,
+      "LiteralEnd": 111,
+      "Literal": "{\"blueprint_hash\":\"abc123\"}"
+    },
+    "SubQuery": {
+      "HasParen": false,
+      "Select": {
+        "SelectPos": 116,
+        "StatementEnd": 156,
+        "With": null,
+        "Top": null,
+        "HasDistinct": false,
+        "DistinctOn": null,
+        "SelectItems": [
+          {
+            "Expr": {
+              "Name": "id",
+              "QuoteType": 1,
+              "NamePos": 127,
+              "NameEnd": 129
+            },
+            "Modifiers": [],
+            "Alias": null
+          },
+          {
+            "Expr": {
+              "Name": "name",
+              "QuoteType": 1,
+              "NamePos": 135,
+              "NameEnd": 139
+            },
+            "Modifiers": [],
+            "Alias": null
+          }
+        ],
+        "From": {
+          "FromPos": 140,
+          "Expr": {
+            "Table": {
+              "TablePos": 145,
+              "TableEnd": 156,
+              "Alias": null,
+              "Expr": {
+                "Database": {
+                  "Name": "db",
+                  "QuoteType": 1,
+                  "NamePos": 145,
+                  "NameEnd": 147
+                },
+                "Table": {
+                  "Name": "my_table",
+                  "QuoteType": 1,
+                  "NamePos": 148,
+                  "NameEnd": 156
+                }
+              },
+              "HasFinal": false
+            },
+            "StatementEnd": 156,
+            "SampleRatio": null,
+            "HasFinal": false
+          }
+        },
+        "Window": null,
+        "Prewhere": null,
+        "Where": null,
+        "GroupBy": null,
+        "WithTotal": false,
+        "Having": null,
+        "OrderBy": null,
+        "LimitBy": null,
+        "Limit": null,
+        "Settings": null,
+        "Format": null,
+        "UnionAll": null,
+        "UnionDistinct": null,
+        "Except": null
+      }
+    }
+  }
+]
diff --git a/parser/testdata/query/output/create_window_view.sql.golden.json b/parser/testdata/query/output/create_window_view.sql.golden.json
@@ -16,6 +16,7 @@
     "UUID": null,
     "OnCluster": null,
     "TableSchema": null,
+    "Comment": null,
     "SubQuery": {
       "HasParen": false,
       "Select": {
diff --git a/parser/walk.go b/parser/walk.go
@@ -641,6 +641,9 @@ func Walk(node Expr, fn WalkFunc) bool {
 		if !Walk(n.TableSchema, fn) {
 			return false
 		}
+		if !Walk(n.Comment, fn) {
+			return false
+		}
 		if !Walk(n.SubQuery, fn) {
 			return false
 		}

Original file line number	Diff line number	Diff line change
`@@ -1452,6 +1452,7 @@ type CreateView struct {`
`1452`	`1452`	`UUID *UUID`
`1453`	`1453`	`OnCluster *ClusterClause`
`1454`	`1454`	`TableSchema *TableSchemaClause`
	`1455`	`+ Comment *StringLiteral`
`1455`	`1456`	`SubQuery *SubQuery`
`1456`	`1457`	`}`
`1457`	`1458`
`@@ -1488,6 +1489,11 @@ func (c *CreateView) Accept(visitor ASTVisitor) error {`
`1488`	`1489`	`return err`
`1489`	`1490`	`}`
`1490`	`1491`	`}`
	`1492`	`+ if c.Comment != nil {`
	`1493`	`+ if err := c.Comment.Accept(visitor); err != nil {`
	`1494`	`+ return err`
	`1495`	`+ }`
	`1496`	`+ }`
`1491`	`1497`	`if c.SubQuery != nil {`
`1492`	`1498`	`if err := c.SubQuery.Accept(visitor); err != nil {`
`1493`	`1499`	`return err`
Original file line number	Diff line number	Diff line change
`@@ -34,6 +34,7 @@`
`34`	`34`	`}`
`35`	`35`	`},`
`36`	`36`	`"TableSchema": null,`
	`37`	`+ "Comment": null,`
`37`	`38`	`"SubQuery": {`
`38`	`39`	`"HasParen": true,`
`39`	`40`	`"Select": {`