comparer

Documentation

Overview

Package comparer provides schema comparison and difference detection for MySQL and PostgreSQL databases.

Overview

The comparer package analyzes two DatabaseSchema objects and produces a detailed list of differences, including:

• Added, removed, and modified tables
• Column changes (type, constraints, defaults)
• Index additions, removals, and modifications
• Foreign key constraint changes
• View, function, procedure changes
• Database-specific objects (triggers, events, sequences, etc.)

Usage

Basic comparison:

diffs, err := comparer.CompareSchemas(oldSchema, newSchema, nil)
if err != nil {
    return err
}

for _, diff := range diffs {
    fmt.Printf("%s: %s\n", diff.Type, diff.Message)
}

Comparison with options:

options := &comparer.CompareOptions{
    IgnoreTables: []string{"temp_*", "cache_*"},
    CompareData:  false,
}
diffs, err := comparer.CompareSchemas(oldSchema, newSchema, options)

Comparison Engines

The package uses database-specific comparison engines (MySQL and PostgreSQL) that understand the nuances of each database system. These engines handle:

• Type compatibility (e.g., VARCHAR vs TEXT)
• Default value formatting
• Expression normalization
• Database-specific features

Integration Tests

The package includes comprehensive integration tests that verify comparison accuracy against real MySQL and PostgreSQL databases using testcontainers.

Index

• func CompareSchemasDetailed(oldSchema, newSchema *schemaextract.DatabaseSchema, opts *CompareOptions) (*diff.MetadataDiff, error)
• func ConvertYesNo(s string) (bool, error)
• func FormatErrorWithQuery(err error, query string) error
• type CompareOptions
  • func DefaultCompareOptions(eng engine.Engine) *CompareOptions

Functions

func CompareSchemasDetailed

func CompareSchemasDetailed(
	oldSchema, newSchema *schemaextract.DatabaseSchema,
	opts *CompareOptions,
) (*diff.MetadataDiff, error)

CompareSchemasDetailed compares two database schemas and returns detailed differences. This is the main entry point for engine-aware schema comparison.

func ConvertYesNo

func ConvertYesNo(s string) (bool, error)

ConvertYesNo converts MySQL/PostgreSQL YES/NO strings to bool.

func FormatErrorWithQuery

func FormatErrorWithQuery(err error, query string) error

FormatErrorWithQuery wraps an error with the SQL query that caused it.

Types

type CompareOptions

type CompareOptions struct {
	// Engine specifies which database engine to use for comparison.
	Engine engine.Engine

	// IgnoreComments ignores comment differences.
	IgnoreComments bool

	// IgnoreCharset ignores charset differences (MySQL).
	IgnoreCharset bool

	// IgnoreCollation ignores collation differences.
	IgnoreCollation bool
}

CompareOptions configures schema comparison behavior.

func DefaultCompareOptions

func DefaultCompareOptions(eng engine.Engine) *CompareOptions

DefaultCompareOptions returns default comparison options.