feat(parser): Snowflake USE and DESCRIBE object-kind prefixes (#483) (#491)

Co-authored-by: Ajit Pratap Singh <ajitpratapsingh@Ajits-Mac-mini-2655.local>

Author: ajitpratap0

pkg/sql/parser/mysql.go

@@ -164,6 +164,23 @@ func (p *Parser) parseDescribeStatement() (ast.Statement, error) {
 		return desc, nil
 	}
 
+	// Snowflake: DESCRIBE TABLE <name>, DESCRIBE VIEW <name>, DESCRIBE STAGE
+	// <name>, etc. Also MySQL's DESCRIBE <db>.<table>. Accept and consume a
+	// leading object-kind keyword (TABLE, VIEW, DATABASE, SCHEMA) before the
+	// name so we don't fail on "DESCRIBE TABLE users".
+	if p.isType(models.TokenTypeTable) || p.isType(models.TokenTypeView) ||
+		p.isType(models.TokenTypeDatabase) ||
+		strings.EqualFold(p.currentToken.Token.Value, "SCHEMA") ||
+		strings.EqualFold(p.currentToken.Token.Value, "STAGE") ||
+		strings.EqualFold(p.currentToken.Token.Value, "STREAM") ||
+		strings.EqualFold(p.currentToken.Token.Value, "TASK") ||
+		strings.EqualFold(p.currentToken.Token.Value, "PIPE") ||
+		strings.EqualFold(p.currentToken.Token.Value, "FUNCTION") ||
+		strings.EqualFold(p.currentToken.Token.Value, "PROCEDURE") ||
+		strings.EqualFold(p.currentToken.Token.Value, "WAREHOUSE") {
+		p.advance()
+	}
+
 	name, err := p.parseQualifiedName()
 	if err != nil {
 		return nil, p.expectedError("table name")

pkg/sql/parser/parser.go

@@ -691,7 +691,9 @@ func (p *Parser) parseStatement() (ast.Statement, error) {
 	case models.TokenTypeShow:
 		p.advance()
 		return p.parseShowStatement()
-	case models.TokenTypeDescribe, models.TokenTypeExplain:
+	case models.TokenTypeDescribe, models.TokenTypeExplain, models.TokenTypeDesc:
+		// DESC is the ORDER-BY sort-direction token but also a synonym for
+		// DESCRIBE at statement position (Oracle, Snowflake, MySQL).
 		p.advance()
 		return p.parseDescribeStatement()
 	case models.TokenTypeReplace:
@@ -713,10 +715,39 @@ func (p *Parser) parseStatement() (ast.Statement, error) {
 			p.advance()
 			return p.parsePragmaStatement()
 		}
+		// Snowflake session-context switches: USE [WAREHOUSE|DATABASE|SCHEMA|ROLE] <name>.
+		// USE is not tokenized as a keyword; dispatch by value in the Snowflake dialect.
+		if p.dialect == string(keywords.DialectSnowflake) &&
+			strings.EqualFold(p.currentToken.Token.Value, "USE") {
+			return p.parseSnowflakeUseStatement()
+		}
 	}
 	return nil, p.expectedError("statement")
 }
 
+// parseSnowflakeUseStatement parses:
+//
+//	USE [WAREHOUSE | DATABASE | SCHEMA | ROLE] <name>
+//
+// The object-kind keyword is optional (plain "USE <name>" switches the current
+// database). We parse-only; the statement is represented as a DescribeStatement
+// placeholder until a dedicated UseStatement node is introduced.
+func (p *Parser) parseSnowflakeUseStatement() (ast.Statement, error) {
+	p.advance() // Consume USE
+	// Optional object kind.
+	switch strings.ToUpper(p.currentToken.Token.Value) {
+	case "WAREHOUSE", "DATABASE", "SCHEMA", "ROLE":
+		p.advance()
+	}
+	name, err := p.parseQualifiedName()
+	if err != nil {
+		return nil, p.expectedError("name after USE")
+	}
+	stmt := ast.GetDescribeStatement()
+	stmt.TableName = "USE " + name
+	return stmt, nil
+}
+
 // NewParser creates a new parser with optional configuration.
 func NewParser(opts ...ParserOption) *Parser {
 	p := &Parser{}

pkg/sql/parser/snowflake_top_level_stmts_test.go

@@ -0,0 +1,39 @@
+// Copyright 2026 GoSQLX Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+
+package parser_test
+
+import (
+	"testing"
+
+	"github.com/ajitpratap0/GoSQLX/pkg/gosqlx"
+	"github.com/ajitpratap0/GoSQLX/pkg/sql/keywords"
+)
+
+// TestSnowflakeUseAndDescribe verifies Snowflake session-context statements
+// (USE WAREHOUSE/DATABASE/SCHEMA/ROLE) and DESCRIBE/DESC with object-kind
+// prefixes. Regression for #483.
+func TestSnowflakeUseAndDescribe(t *testing.T) {
+	queries := []string{
+		`USE WAREHOUSE compute_wh`,
+		`USE DATABASE my_db`,
+		`USE SCHEMA analytics`,
+		`USE ROLE analyst`,
+		`USE my_db`,
+		`USE my_db.public`,
+		`DESCRIBE TABLE users`,
+		`DESCRIBE VIEW user_summary`,
+		`DESCRIBE STAGE my_stage`,
+		`DESC TABLE users`,
+		`DESC users`,
+	}
+	for _, q := range queries {
+		q := q
+		t.Run(q, func(t *testing.T) {
+			if _, err := gosqlx.ParseWithDialect(q, keywords.DialectSnowflake); err != nil {
+				t.Fatalf("parse failed: %v", err)
+			}
+		})
+	}
+}