GoWeb/database/migrate.go

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package database
import (
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"GoWeb/internal"
"errors"
"fmt"
"github.com/lib/pq"
"log/slog"
"reflect"
)
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// Migrate given a dummy object of any type, it will create a table with the same name
// as the type and create columns with the same name as the fields of the object
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func Migrate(app *app.Deps, anyStruct interface{}) error {
valueOfStruct := reflect.ValueOf(anyStruct)
typeOfStruct := valueOfStruct.Type()
tableName := typeOfStruct.Name()
err := createTable(app, tableName)
if err != nil {
return err
}
for i := 0; i < valueOfStruct.NumField(); i++ {
fieldType := typeOfStruct.Field(i)
fieldName := fieldType.Name
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// Create column if dummy for migration is NOT zero value
fieldValue := valueOfStruct.Field(i).Interface()
if !reflect.ValueOf(fieldValue).IsZero() {
if fieldName != "Id" && fieldName != "id" {
err := createColumn(app, tableName, fieldName, fieldType.Type.Name())
if err != nil {
return err
}
}
}
}
return nil
}
// createTable creates a table with the given name if it doesn't exist, it is assumed that id will be the primary key
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func createTable(app *app.Deps, tableName string) error {
var tableExists bool
err := app.Db.QueryRow("SELECT EXISTS (SELECT 1 FROM pg_catalog.pg_class c JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace WHERE c.relname ~ $1 AND pg_catalog.pg_table_is_visible(c.oid))", "^"+tableName+"$").Scan(&tableExists)
if err != nil {
slog.Error("error checking if table exists: " + tableName)
return err
}
if tableExists {
slog.Info("table already exists: " + tableName)
return nil
} else {
sanitizedTableQuery := fmt.Sprintf("CREATE TABLE IF NOT EXISTS \"%s\" (\"Id\" serial primary key)", tableName)
_, err := app.Db.Query(sanitizedTableQuery)
if err != nil {
slog.Error("error creating table: " + tableName)
return err
}
slog.Info("table created successfully: " + tableName)
return nil
}
}
// createColumn creates a column with the given name and type if it doesn't exist
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func createColumn(app *app.Deps, tableName, columnName, columnType string) error {
var columnExists bool
err := app.Db.QueryRow("SELECT EXISTS (SELECT 1 FROM information_schema.columns WHERE table_name = $1 AND column_name = $2)", tableName, columnName).Scan(&columnExists)
if err != nil {
slog.Error("error checking if column exists: " + columnName + " in table: " + tableName)
return err
}
if columnExists {
slog.Info("column already exists: " + columnName + " in table: " + tableName)
return nil
} else {
postgresType, err := getPostgresType(columnType)
if err != nil {
slog.Error("error creating column: " + columnName + " in table: " + tableName + " with type: " + postgresType)
return err
}
sanitizedTableName := pq.QuoteIdentifier(tableName)
query := fmt.Sprintf("ALTER TABLE %s ADD COLUMN IF NOT EXISTS \"%s\" %s", sanitizedTableName, columnName, postgresType)
_, err = app.Db.Query(query)
if err != nil {
slog.Error("error creating column: " + columnName + " in table: " + tableName + " with type: " + postgresType)
return err
}
slog.Info("column created successfully:", columnName)
return nil
}
}
// Given a type in Go, return the corresponding type in Postgres
func getPostgresType(goType string) (string, error) {
switch goType {
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case "int", "int32", "uint", "uint32":
return "integer", nil
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case "int64", "uint64":
return "bigint", nil
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case "int16", "int8", "uint16", "uint8", "byte":
return "smallint", nil
case "string":
return "text", nil
case "float64":
return "double precision", nil
case "bool":
return "boolean", nil
case "Time":
return "timestamp", nil
case "[]byte":
return "bytea", nil
}
return "", errors.New("Unknown type: " + goType)
}