Add support for CREATE DICTIONARY statement

[Copilot]

This PR implements comprehensive support for ClickHouse CREATE DICTIONARY statements based on the official ClickHouse grammar specification.

Features Implemented

Core Syntax Support

• CREATE [OR REPLACE] DICTIONARY [IF NOT EXISTS] name [UUID 'uuid'] [ON CLUSTER cluster]
• Full dictionary schema with attribute definitions and properties
• All dictionary engine clauses with proper validation

Dictionary Attributes

• Basic attribute definition: name Type
• DEFAULT literal - default value for attribute
• EXPRESSION columnExpr - computed attribute expression
• HIERARCHICAL - hierarchical dictionary attribute
• INJECTIVE - injective mapping attribute
• IS_OBJECT_ID - object ID attribute
• Support for multiple properties per attribute

Dictionary Engine Clauses

• PRIMARY KEY columnExprList - optional primary key definition
• SOURCE(sourceName(args...)) - required data source configuration
• LIFETIME(value) or LIFETIME(MIN min MAX max) - cache lifetime
• LAYOUT(layoutName(args...)) - dictionary layout configuration
• RANGE(MIN minCol MAX maxCol) - range dictionary configuration
• SETTINGS(name=value, ...) - dictionary-specific settings with parentheses

Examples

Basic Dictionary

CREATE DICTIONARY test.my_dict (
    id UInt64,
    name String DEFAULT '',
    value Float64 EXPRESSION toFloat64OrZero(name)
)
PRIMARY KEY id
SOURCE(MYSQL(host 'localhost' port 3306 db 'test' table 'data'))
LIFETIME(MIN 1000 MAX 2000)
LAYOUT(HASHED())
SETTINGS(max_block_size = 8192);

Complex Dictionary with All Features

CREATE OR REPLACE DICTIONARY test.complex_dict 
UUID '12345678-1234-1234-1234-123456789012'
ON CLUSTER production_cluster
(
    id UInt64 HIERARCHICAL INJECTIVE,
    name String DEFAULT '' EXPRESSION toString(id),
    object_id UInt64 IS_OBJECT_ID
)
PRIMARY KEY id
SOURCE(MYSQL(host 'localhost' port 3306 user 'root' password 'secret'))
LIFETIME(MIN 600 MAX 1200)
LAYOUT(CACHE(size_in_cells 1000))
RANGE(MIN start_date MAX end_date)
SETTINGS(max_block_size=8192, max_insert_block_size=1048576);

Implementation Details

• Added CreateDictionary AST node with complete visitor support
• Implemented dictionary-specific parsing functions for all clauses
• Added proper string formatting that maintains ClickHouse compatibility
• Integrated into existing DDL parser infrastructure
• Added comprehensive test coverage with golden file validation

Testing

• ✅ Comprehensive parsing tests for all dictionary features
• ✅ Round-trip formatting validation (parse → format → parse)
• ✅ Complex real-world dictionary examples
• ✅ All existing tests continue to pass

Fixes #12.

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[coveralls]

Pull Request Test Coverage Report for Build 16347549962

Details

• 503 of 929 (54.14%) changed or added relevant lines in 3 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.7%) to 63.224%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
parser/ast_visitor.go	27	50	54.0%
parser/ast.go	221	396	55.81%
parser/parser_table.go	255	483	52.8%

Files with Coverage Reduction	New Missed Lines	%
parser/parser_table.go	1	65.22%

Totals
Change from base Build 16210909526:	-0.7%
Covered Lines:	8092
Relevant Lines:	12799

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💛 - Coveralls