Constraint System

/**
 * Complete constraint trait specification
 * Represents three-dimensional constraint behavior: enable/disable, validate/no-validate, rely/no-rely
 */
public class SqlHiveConstraintTrait {
    /**
     * Creates a constraint trait with all three dimensions
     * @param enable Enable or disable literal (ENABLE/DISABLE)
     * @param validate Validate or no-validate literal (VALIDATE/NOVALIDATE)  
     * @param rely Rely or no-rely literal (RELY/NORELY)
     */
    public SqlHiveConstraintTrait(SqlLiteral enable, SqlLiteral validate, SqlLiteral rely);

    /**
     * Converts constraint trait to SQL representation
     * @param writer SQL writer for output
     * @param leftPrec Left precedence
     * @param rightPrec Right precedence
     */
    public void unparse(SqlWriter writer, int leftPrec, int rightPrec);

    /**
     * Checks if constraint is enabled
     * @return true if constraint is enabled, false otherwise
     */
    public boolean isEnable();

    /**
     * Checks if constraint validation is enabled
     * @return true if constraint validation is enabled, false otherwise
     */
    public boolean isValidate();

    /**
     * Checks if constraint rely is enabled
     * @return true if constraint rely is enabled, false otherwise
     */
    public boolean isRely();
}

/**
 * Constraint enable/disable options
 * Controls whether the constraint is active
 */
public enum SqlHiveConstraintEnable {
    /** Enable the constraint */
    ENABLE,
    
    /** Disable the constraint */
    DISABLE;

    /**
     * Creates SQL literal symbol for the enable state
     * @param pos Parser position information
     * @return SqlLiteral representing the enable state
     */
    public SqlLiteral symbol(SqlParserPos pos);
}

/**
 * Constraint validate/no-validate options
 * Controls whether constraint validation occurs during data operations
 */
public enum SqlHiveConstraintValidate {
    /** Validate constraint during data operations */
    VALIDATE,
    
    /** Do not validate constraint during data operations */
    NOVALIDATE;

    /**
     * Creates SQL literal symbol for the validation state
     * @param pos Parser position information
     * @return SqlLiteral representing the validation state
     */
    public SqlLiteral symbol(SqlParserPos pos);
}

/**
 * Constraint rely/no-rely options
 * Controls whether the optimizer can rely on the constraint for query optimization
 */
public enum SqlHiveConstraintRely {
    /** Optimizer can rely on the constraint */
    RELY,
    
    /** Optimizer cannot rely on the constraint */
    NORELY;

    /**
     * Creates SQL literal symbol for the rely state
     * @param pos Parser position information
     * @return SqlLiteral representing the rely state
     */
    public SqlLiteral symbol(SqlParserPos pos);
}

// Create constraint traits programmatically
SqlParserPos pos = SqlParserPos.ZERO;

// Create ENABLE VALIDATE RELY trait (default/recommended)
SqlLiteral enable = SqlHiveConstraintEnable.ENABLE.symbol(pos);
SqlLiteral validate = SqlHiveConstraintValidate.VALIDATE.symbol(pos);
SqlLiteral rely = SqlHiveConstraintRely.RELY.symbol(pos);

SqlHiveConstraintTrait defaultTrait = new SqlHiveConstraintTrait(enable, validate, rely);

// Create DISABLE NOVALIDATE NORELY trait (minimal constraint)
SqlLiteral disable = SqlHiveConstraintEnable.DISABLE.symbol(pos);
SqlLiteral novalidate = SqlHiveConstraintValidate.NOVALIDATE.symbol(pos);
SqlLiteral norely = SqlHiveConstraintRely.NORELY.symbol(pos);

SqlHiveConstraintTrait minimalTrait = new SqlHiveConstraintTrait(disable, novalidate, norely);

// Check trait properties
boolean isEnabled = defaultTrait.isEnable();        // true
boolean isValidated = defaultTrait.isValidate();    // true
boolean isReliable = defaultTrait.isRely();         // true

boolean isDisabled = minimalTrait.isEnable();       // false
boolean isNotValidated = minimalTrait.isValidate(); // false
boolean isNotReliable = minimalTrait.isRely();      // false

-- Table creation with constraints and traits
CREATE TABLE customer_data (
    customer_id BIGINT,
    email STRING,
    phone STRING,
    registration_date DATE,
    
    -- Primary key with default trait (ENABLE VALIDATE RELY)
    PRIMARY KEY (customer_id) ENABLE VALIDATE RELY,
    
    -- NOT NULL constraint with custom trait
    CONSTRAINT nn_email NOT NULL (email) ENABLE NOVALIDATE RELY,
    
    -- Unique constraint with minimal enforcement
    CONSTRAINT uk_email UNIQUE (email) DISABLE NOVALIDATE NORELY
);

-- Alter table to modify constraint traits
ALTER TABLE customer_data 
CHANGE CONSTRAINT nn_email 
NOT NULL (email) ENABLE VALIDATE RELY;

// Default constraint trait (ENABLE NOVALIDATE RELY)
byte defaultTrait = HiveDDLUtils.defaultTrait();

// Modify traits
byte enabledTrait = HiveDDLUtils.enableConstraint(defaultTrait);
byte disabledTrait = HiveDDLUtils.disableConstraint(defaultTrait);
byte validatedTrait = HiveDDLUtils.validateConstraint(defaultTrait);
byte nonValidatedTrait = HiveDDLUtils.noValidateConstraint(defaultTrait);
byte reliableTrait = HiveDDLUtils.relyConstraint(defaultTrait);
byte nonReliableTrait = HiveDDLUtils.noRelyConstraint(defaultTrait);

// Check trait properties
boolean requiresEnable = HiveDDLUtils.requireEnableConstraint(defaultTrait);
boolean requiresValidate = HiveDDLUtils.requireValidateConstraint(defaultTrait);
boolean requiresRely = HiveDDLUtils.requireRelyConstraint(defaultTrait);

// Encode constraint trait object to byte representation
SqlHiveConstraintTrait traitObj = new SqlHiveConstraintTrait(enable, validate, rely);
byte encodedTrait = HiveDDLUtils.encodeConstraintTrait(traitObj);

// Create table with primary key constraint
String createTableWithPKSql = """
    CREATE TABLE orders (
        order_id BIGINT,
        customer_id BIGINT,
        order_date DATE,
        total_amount DECIMAL(10,2),
        
        -- Primary key with full enforcement
        CONSTRAINT pk_order PRIMARY KEY (order_id) ENABLE VALIDATE RELY
    )
    TBLPROPERTIES (
        'hive.pk.constraint.trait' = 'ENABLE_VALIDATE_RELY'
    )
    """;

// Programmatic primary key creation
HiveTableCreationContext context = new HiveTableCreationContext();
context.pkTrait = new SqlHiveConstraintTrait(
    SqlHiveConstraintEnable.ENABLE.symbol(pos),
    SqlHiveConstraintValidate.VALIDATE.symbol(pos),
    SqlHiveConstraintRely.RELY.symbol(pos)
);

// Create table with NOT NULL constraints
String createTableWithNotNullSql = """
    CREATE TABLE customer_profile (
        customer_id BIGINT NOT NULL ENABLE VALIDATE RELY,
        first_name STRING NOT NULL ENABLE NOVALIDATE RELY,
        last_name STRING NOT NULL ENABLE NOVALIDATE RELY,
        email STRING NOT NULL DISABLE NOVALIDATE NORELY,
        phone STRING,
        registration_date DATE NOT NULL ENABLE VALIDATE RELY
    )
    """;

// Programmatic NOT NULL constraint creation
HiveTableCreationContext context = new HiveTableCreationContext();

// Create NOT NULL traits for multiple columns
context.notNullTraits = List.of(
    new SqlHiveConstraintTrait(
        SqlHiveConstraintEnable.ENABLE.symbol(pos),
        SqlHiveConstraintValidate.VALIDATE.symbol(pos),
        SqlHiveConstraintRely.RELY.symbol(pos)
    ),
    new SqlHiveConstraintTrait(
        SqlHiveConstraintEnable.ENABLE.symbol(pos),
        SqlHiveConstraintValidate.NOVALIDATE.symbol(pos),
        SqlHiveConstraintRely.RELY.symbol(pos)
    )
);

context.notNullCols = List.of(
    new SqlIdentifier("customer_id", pos),
    new SqlIdentifier("email", pos)
);

public class HiveConstraintManager {
    
    /**
     * Creates a constraint trait for different enforcement levels
     */
    public static SqlHiveConstraintTrait createConstraintTrait(String enforcementLevel, SqlParserPos pos) {
        SqlLiteral enable, validate, rely;
        
        switch (enforcementLevel.toUpperCase()) {
            case "STRICT":
                // Full enforcement: validate data and enable optimizer reliance
                enable = SqlHiveConstraintEnable.ENABLE.symbol(pos);
                validate = SqlHiveConstraintValidate.VALIDATE.symbol(pos);
                rely = SqlHiveConstraintRely.RELY.symbol(pos);
                break;
                
            case "OPTIMIZER_ONLY":
                // Enable for optimizer, but don't validate data
                enable = SqlHiveConstraintEnable.ENABLE.symbol(pos);
                validate = SqlHiveConstraintValidate.NOVALIDATE.symbol(pos);
                rely = SqlHiveConstraintRely.RELY.symbol(pos);
                break;
                
            case "INFORMATIONAL":
                // Metadata only, no enforcement or optimization
                enable = SqlHiveConstraintEnable.DISABLE.symbol(pos);
                validate = SqlHiveConstraintValidate.NOVALIDATE.symbol(pos);
                rely = SqlHiveConstraintRely.NORELY.symbol(pos);
                break;
                
            default: // "STANDARD"
                // Default Hive behavior: enable but don't validate
                enable = SqlHiveConstraintEnable.ENABLE.symbol(pos);
                validate = SqlHiveConstraintValidate.NOVALIDATE.symbol(pos);
                rely = SqlHiveConstraintRely.RELY.symbol(pos);
                break;
        }
        
        return new SqlHiveConstraintTrait(enable, validate, rely);
    }
    
    /**
     * Validates constraint trait combinations
     */
    public static boolean isValidConstraintCombination(SqlHiveConstraintTrait trait) {
        // Validation rules:
        // 1. Cannot validate disabled constraints
        // 2. Cannot rely on disabled constraints
        // 3. Should not rely on non-validated constraints (warning, not error)
        
        if (!trait.isEnable() && trait.isValidate()) {
            return false; // Cannot validate disabled constraint
        }
        
        if (!trait.isEnable() && trait.isRely()) {
            return false; // Cannot rely on disabled constraint
        }
        
        return true;
    }
    
    /**
     * Provides recommendations for constraint traits based on table usage
     */
    public static String recommendConstraintTrait(String tableType, String workloadType) {
        // Recommend constraint traits based on usage patterns
        
        if ("TRANSACTIONAL".equals(tableType)) {
            if ("OLTP".equals(workloadType)) {
                return "STRICT"; // Full validation for transactional workloads
            } else {
                return "STANDARD"; // Enable but don't validate for analytical workloads
            }
        } else if ("ANALYTICAL".equals(tableType)) {
            if ("ETL".equals(workloadType)) {
                return "OPTIMIZER_ONLY"; // Help optimizer without validation overhead
            } else {
                return "INFORMATIONAL"; // Metadata only for ad-hoc queries
            }
        }
        
        return "STANDARD"; // Default recommendation
    }
}

// Usage examples
SqlParserPos pos = SqlParserPos.ZERO;

// Create strict constraint for critical data
SqlHiveConstraintTrait strictTrait = HiveConstraintManager.createConstraintTrait("STRICT", pos);
System.out.println("Strict trait - Enable: " + strictTrait.isEnable() + 
                   ", Validate: " + strictTrait.isValidate() + 
                   ", Rely: " + strictTrait.isRely());

// Validate constraint combination
boolean isValid = HiveConstraintManager.isValidConstraintCombination(strictTrait);
System.out.println("Constraint combination is valid: " + isValid);

// Get recommendation
String recommendation = HiveConstraintManager.recommendConstraintTrait("TRANSACTIONAL", "OLTP");
System.out.println("Recommended constraint level: " + recommendation);

// Evolution of constraint enforcement over time
public class ConstraintEvolution {
    
    /**
     * Migrates constraints from informational to enforced
     */
    public void migrateConstraintsToEnforced(String tableName, TableEnvironment tableEnv) {
        // Step 1: Start with informational constraints (DISABLE NOVALIDATE NORELY)
        String initialConstraintSql = String.format("""
            ALTER TABLE %s 
            ADD CONSTRAINT pk_temp PRIMARY KEY (id) DISABLE NOVALIDATE NORELY
            """, tableName);
        
        // Step 2: Enable constraint for optimizer (ENABLE NOVALIDATE RELY)
        String enableForOptimizerSql = String.format("""
            ALTER TABLE %s 
            CHANGE CONSTRAINT pk_temp PRIMARY KEY (id) ENABLE NOVALIDATE RELY
            """, tableName);
        
        // Step 3: Enable validation after data cleanup (ENABLE VALIDATE RELY)
        String enableValidationSql = String.format("""
            ALTER TABLE %s 
            CHANGE CONSTRAINT pk_temp PRIMARY KEY (id) ENABLE VALIDATE RELY
            """, tableName);
        
        try {
            // Execute migration steps
            tableEnv.executeSql(initialConstraintSql);
            System.out.println("Step 1: Added informational constraint");
            
            // Data quality assessment would happen here
            
            tableEnv.executeSql(enableForOptimizerSql);
            System.out.println("Step 2: Enabled constraint for optimizer");
            
            // Data cleanup and validation would happen here
            
            tableEnv.executeSql(enableValidationSql);
            System.out.println("Step 3: Enabled full constraint validation");
            
        } catch (Exception e) {
            System.err.println("Constraint migration failed: " + e.getMessage());
        }
    }
}