fix implicit select parsing and pivot statement boundaries

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: emrberk

src/index.ts

@@ -41,13 +41,14 @@ export function parseToAst(sql: string): ParseResult {
     });
   }
 
-  if (errors.length > 0) {
-    return { ast: [], errors };
+  let ast: Statement[] = [];
+  try {
+    ast = visitor.visit(cst) as Statement[];
+  } catch (e) {
+    // Visitor may fail on incomplete CST — return what we have
   }
 
-  const ast = visitor.visit(cst) as Statement[];
-
-  return { ast, errors: [] };
+  return { ast, errors };
 }
 
 /**

src/parser/parser.ts

@@ -443,10 +443,7 @@ class QuestDBParser extends CstParser {
         GATE: () => this.LA(1).tokenType === Compile && this.LA(2).tokenType === View,
         ALT: () => this.SUBRULE(this.compileViewStatement),
       },
-      {
-        GATE: this.BACKTRACK(this.implicitSelectStatement),
-        ALT: () => this.SUBRULE(this.implicitSelectStatement),
-      },
+      { ALT: () => this.SUBRULE(this.implicitSelectStatement) },
     ]);
   });
 
@@ -3035,7 +3032,7 @@ class QuestDBParser extends CstParser {
     this.SUBRULE(this.pivotBody);
     this.CONSUME2(RParen);
     this.OPTION2(() => {
-      this.OPTION3(() => this.CONSUME(As));
+      this.CONSUME(As);
       this.SUBRULE6(this.identifier);
     });
     this.OPTION4(() => this.SUBRULE(this.orderByClause));

src/parser/visitor.ts

@@ -323,25 +323,25 @@ class QuestDBVisitor extends BaseVisitor {
       columns: [{ type: "star" } as AST.SelectItem],
     };
     if (ctx.fromClause) {
-      result.from = this.visit(ctx.fromClause);
+      result.from = this.visitSafe(ctx.fromClause);
     }
     if (ctx.whereClause) {
-      result.where = this.visit(ctx.whereClause);
+      result.where = this.visitSafe(ctx.whereClause);
     }
     if (ctx.sampleByClause) {
-      result.sampleBy = this.visit(ctx.sampleByClause);
+      result.sampleBy = this.visitSafe(ctx.sampleByClause);
     }
     if (ctx.latestOnClause) {
-      result.latestOn = this.visit(ctx.latestOnClause);
+      result.latestOn = this.visitSafe(ctx.latestOnClause);
     }
     if (ctx.groupByClause) {
-      result.groupBy = this.visit(ctx.groupByClause);
+      result.groupBy = this.visitSafe(ctx.groupByClause);
     }
     if (ctx.orderByClause) {
-      result.orderBy = this.visit(ctx.orderByClause);
+      result.orderBy = this.visitSafe(ctx.orderByClause);
     }
     if (ctx.limitClause) {
-      result.limit = this.visit(ctx.limitClause);
+      result.limit = this.visitSafe(ctx.limitClause);
     }
     return result;
   }
@@ -2662,6 +2662,15 @@ class QuestDBVisitor extends BaseVisitor {
     }
   }
 
+  /** Visit a CST node, returning undefined instead of throwing on incomplete input */
+  private visitSafe(node: any): any {
+    try {
+      return this.visit(node);
+    } catch {
+      return undefined;
+    }
+  }
+
   /** Get the startOffset of the first token in a CstNode */
   private getFirstTokenOffset(node: any): number {
     if (node.startOffset !== undefined) return node.startOffset;

tests/autocomplete.test.ts

@@ -866,3 +866,24 @@ describe("Expression autocomplete", () => {
     expect(labels).toContain("NOT");
   });
 });
+
+describe("Implicit SELECT autocomplete", () => {
+  it("should suggest columns after implicit select WHERE", () => {
+    const labels = getLabelsAt(provider, "trades WHERE ");
+    expect(labels).toContain("symbol");
+    expect(labels).toContain("price");
+    expect(labels).toContain("NOT");
+    expect(labels).toContain("CASE");
+  });
+
+  it("should suggest keywords after bare table name", () => {
+    const labels = getLabelsAt(provider, "trades ");
+    expect(labels).toContain("WHERE");
+  });
+
+  it("should suggest columns for incomplete implicit select in multi-statement context", () => {
+    const labels = getLabelsAt(provider, "SELECT 1; trades WHERE ");
+    // Should get suggestions even after semicolon with implicit select
+    expect(labels.length).toBeGreaterThan(0);
+  });
+});

tests/parser.test.ts

@@ -1641,6 +1641,38 @@ describe("QuestDB Parser", () => {
     });
   });
 
+  describe("PIVOT multi-statement boundary", () => {
+    it("should parse two consecutive pivot statements as separate statements", () => {
+      const sql = `trades PIVOT (avg(price) FOR symbol IN ('ETH-USDT'))
+trades PIVOT (sum(amount) FOR symbol IN ('BTC-USDT'))`;
+      const result = parseToAst(sql);
+      expect(result.ast).toHaveLength(2);
+      expect(result.ast[0].type).toBe("pivot");
+      expect(result.ast[1].type).toBe("pivot");
+    });
+
+    it("should not consume next table name as alias without AS", () => {
+      const sql = `trades PIVOT (avg(price) FOR symbol IN ('ETH-USDT'))
+orders PIVOT (sum(amount) FOR status IN ('open'))`;
+      const result = parseToAst(sql);
+      expect(result.ast).toHaveLength(2);
+      if (result.ast[0].type === "pivot") {
+        expect(result.ast[0].alias).toBeUndefined();
+      }
+    });
+
+    it("should still support PIVOT alias with AS keyword", () => {
+      const result = parseToAst(
+        "trades PIVOT (avg(price) FOR symbol IN ('ETH-USDT')) AS p"
+      );
+      expect(result.errors).toHaveLength(0);
+      expect(result.ast).toHaveLength(1);
+      if (result.ast[0].type === "pivot") {
+        expect(result.ast[0].alias).toBe("p");
+      }
+    });
+  });
+
   describe("PIVOT round-trip tests", () => {
     const queries = [
       "trades PIVOT (sum(amount) FOR category IN ('food', 'drinks'))",
@@ -3220,6 +3252,40 @@ describe("QuestDB Parser", () => {
     });
   });
 
+  describe("Incomplete implicit SELECT produces partial AST", () => {
+    it("should produce AST for incomplete 'table WHERE'", () => {
+      const result = parseToAst("core_price WHERE ");
+      // Should produce a partial AST even though the query is incomplete
+      expect(result.ast.length).toBeGreaterThan(0);
+      const stmt = result.ast[0] as any;
+      expect(stmt.type).toBe("select");
+      expect(stmt.implicit).toBe(true);
+    });
+
+    it("should produce AST with table reference for incomplete implicit select", () => {
+      const result = parseToAst("trades WHERE price > ");
+      expect(result.ast.length).toBeGreaterThan(0);
+      const stmt = result.ast[0] as any;
+      expect(stmt.type).toBe("select");
+      expect(stmt.implicit).toBe(true);
+    });
+
+    it("should produce AST for bare table name only", () => {
+      const result = parseToAst("trades");
+      expect(result.ast.length).toBeGreaterThan(0);
+      const stmt = result.ast[0] as any;
+      expect(stmt.type).toBe("select");
+      expect(stmt.implicit).toBe(true);
+    });
+
+    it("should produce AST for incomplete implicit select after semicolon", () => {
+      const result = parseToAst("SELECT 1; core_price WHERE ");
+      expect(result.ast.length).toBeGreaterThan(0);
+      // First statement is complete SELECT
+      expect(result.ast[0].type).toBe("select");
+    });
+  });
+
   describe("Parenthesized SHOW as table source", () => {
     it("should parse (SHOW PARAMETERS) WHERE ...", () => {
       const result = parseToAst(

yarn.lock

@@ -349,6 +349,18 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@questdb/questdb-sql-parser@workspace:.":
+  version: 0.0.0-use.local
+  resolution: "@questdb/questdb-sql-parser@workspace:."
+  dependencies:
+    "@types/jest": "npm:^30.0.0"
+    "@types/node": "npm:^25.2.0"
+    chevrotain: "npm:^11.1.1"
+    typescript: "npm:^5.9.3"
+    vitest: "npm:^4.0.18"
+  languageName: unknown
+  linkType: soft
+
 "@rollup/rollup-android-arm-eabi@npm:4.57.1":
   version: 4.57.1
   resolution: "@rollup/rollup-android-arm-eabi@npm:4.57.1"
@@ -1546,18 +1558,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"questdb-sql-parser@workspace:.":
-  version: 0.0.0-use.local
-  resolution: "questdb-sql-parser@workspace:."
-  dependencies:
-    "@types/jest": "npm:^30.0.0"
-    "@types/node": "npm:^25.2.0"
-    chevrotain: "npm:^11.1.1"
-    typescript: "npm:^5.9.3"
-    vitest: "npm:^4.0.18"
-  languageName: unknown
-  linkType: soft
-
 "react-is@npm:^18.3.1":
   version: 18.3.1
   resolution: "react-is@npm:18.3.1"