Package liquibase.sqlgenerator

Interface SqlGenerator<T extends SqlStatement>

Type Parameters:
T - Used to specify which type of SqlStatement this generator supports. If it supports multiple SqlStatement types, pass SqlStatement. The SqlGeneratorFactory will use this parameter to augment the response from the supports() method
All Superinterfaces:
PrioritizedService
All Known Implementing Classes:
AbstractSqlGenerator, AddAutoIncrementGenerator, AddAutoIncrementGeneratorDB2, AddAutoIncrementGeneratorHsqlH2, AddAutoIncrementGeneratorInformix, AddAutoIncrementGeneratorMySQL, AddAutoIncrementGeneratorSQLite, AddColumnGenerator, AddColumnGeneratorDefaultClauseBeforeNotNull, AddColumnGeneratorSQLite, AddDefaultValueGenerator, AddDefaultValueGeneratorDerby, AddDefaultValueGeneratorInformix, AddDefaultValueGeneratorMSSQL, AddDefaultValueGeneratorMySQL, AddDefaultValueGeneratorOracle, AddDefaultValueGeneratorPostgres, AddDefaultValueGeneratorSQLite, AddDefaultValueGeneratorSybase, AddDefaultValueGeneratorSybaseASA, AddForeignKeyConstraintGenerator, AddPrimaryKeyGenerator, AddPrimaryKeyGeneratorInformix, AddUniqueConstraintGenerator, AddUniqueConstraintGeneratorInformix, AddUniqueConstraintGeneratorTDS, AlterSequenceGenerator, BatchDmlExecutablePreparedStatementGenerator, ClearDatabaseChangeLogTableGenerator, CommentGenerator, CopyRowsGenerator, CreateDatabaseChangeLogLockTableGenerator, CreateDatabaseChangeLogTableGenerator, CreateDatabaseChangeLogTableGeneratorSybase, CreateIndexGenerator, CreateIndexGeneratorFirebird, CreateIndexGeneratorPostgres, CreateProcedureGenerator, CreateSequenceGenerator, CreateSequenceGeneratorSnowflake, CreateTableGenerator, CreateTableGeneratorInformix, CreateViewGenerator, CreateViewGeneratorInformix, DeleteGenerator, DropColumnGenerator, DropDefaultValueGenerator, DropDefaultValueGeneratorSnowflake, DropForeignKeyConstraintGenerator, DropIndexGenerator, DropPrimaryKeyGenerator, DropProcedureGenerator, DropProcedureGeneratorSnowflake, DropSequenceGenerator, DropTableGenerator, DropUniqueConstraintGenerator, DropViewGenerator, GetNextChangeSetSequenceValueGenerator, GetViewDefinitionGenerator, GetViewDefinitionGeneratorDB2, GetViewDefinitionGeneratorDerby, GetViewDefinitionGeneratorFirebird, GetViewDefinitionGeneratorHsql, GetViewDefinitionGeneratorInformix, GetViewDefinitionGeneratorMSSQL, GetViewDefinitionGeneratorOracle, GetViewDefinitionGeneratorPostgres, GetViewDefinitionGeneratorSnowflake, GetViewDefinitionGeneratorSybase, GetViewDefinitionGeneratorSybaseASA, InitializeDatabaseChangeLogLockTableGenerator, InsertDataChangeGenerator, InsertGenerator, InsertOrUpdateGenerator, InsertOrUpdateGeneratorDB2, InsertOrUpdateGeneratorH2, InsertOrUpdateGeneratorHsql, InsertOrUpdateGeneratorInformix, InsertOrUpdateGeneratorMSSQL, InsertOrUpdateGeneratorMySQL, InsertOrUpdateGeneratorOracle, InsertOrUpdateGeneratorPostgres, InsertOrUpdateGeneratorSnowflake, InsertOrUpdateGeneratorSQLite, InsertOrUpdateGeneratorSybaseASA, InsertSetGenerator, LockDatabaseChangeLogGenerator, MarkChangeSetRanGenerator, ModifyDataTypeGenerator, RawParameterizedSqlGenerator, RawSqlGenerator, ReindexGeneratorSQLite, RemoveChangeSetRanStatusGenerator, RenameColumnGenerator, RenameSequenceGenerator, RenameTableGenerator, RenameTableGeneratorSnowflake, RenameViewGenerator, RenameViewGeneratorSnowflake, ReorganizeTableGeneratorDB2, RuntimeGenerator, SelectFromDatabaseChangeLogGenerator, SelectFromDatabaseChangeLogLockGenerator, SetColumnRemarksGenerator, SetColumnRemarksGeneratorSnowflake, SetNullableGenerator, SetTableRemarksGenerator, SetTableRemarksGeneratorSnowflake, SetViewRemarksGenerator, StoredProcedureGenerator, TableIsEmptyGenerator, TableRowCountGenerator, TagDatabaseGenerator, UnlockDatabaseChangeLogGenerator, UpdateChangeSetChecksumGenerator, UpdateDataChangeGenerator, UpdateGenerator
public interface SqlGenerator<T extends SqlStatement> extends PrioritizedService
SqlGenerator implementations take a database-independent SqlStatement interface and create a database-specific Sql object. SqlGenerators are registered with the SqlGeneratorFactory, which is used to determine the correct generator to use for a given statement/database combination.

The SqlGenerator implementations are responsible for determining whether the data contained in the SqlStatement method is valid using the validate method.

Naming Conventions:
Default SqlGenerators for a particular SqlStatement use the same name as the SqlStatement class, replacing "Statement" with "Generator" (e.g.: CreateTableStatement -> CreateTableGenerator). Database-specific or alternate SqlGenerators append a description of what makes them different appended (e.g. CreateTableStatement -> CreateTableGeneratorOracle)

NOTE: There is only one instance of each SqlGenerator implementation created, and they must be thread safe.

Lifecycle:

  1. Instance of SqlGenerator subclass is created when registered with SqlGeneratorFactory
  2. For each SqlStatement to execute, SqlGeneratorFactory calls supports() to determine if the given SqlGenerator will work for the current SqlStatement/Database combination
  3. SqlGeneratorFactory calls getPriority to determine which of all the SqlGenerators that support a given SqlStatement/Database combination is the best to use.
  4. Liquibase calls validate() on the best SqlGenerator to determine if the data contained in the SqlStatement is correct and complete for the given Database
  5. If validate returns a no-error ValidationErrors object, Liquibase will call the generateSql() method and execute the resulting SQL against the database.
See Also:

  • Field Details

    • PRIORITY_DEFAULT

      static final int PRIORITY_DEFAULT
      See Also:

    • PRIORITY_DATABASE

      static final int PRIORITY_DATABASE
      See Also:

    • EMPTY_SQL

      static final Sql[] EMPTY_SQL
      Represent an empty array of Sql.

  • Method Details

    • getPriority

      int getPriority()
      Of all the SqlGenerators that "support" a given SqlStatement/Database, SqlGeneratorFactory will return the one with the highest priority.
      Specified by:
      getPriority in interface PrioritizedService

    • supports

      boolean supports(T statement, Database database)
      Does this generator support the given statement/database combination? Do not validate the statement with this method, only return if it can support it.

    • generateStatementsIsVolatile

      boolean generateStatementsIsVolatile(Database database)
      Does this change require access to the database metadata? If true, the change cannot be used in an updateSql-style command.

    • generateRollbackStatementsIsVolatile

      boolean generateRollbackStatementsIsVolatile(Database database)

    • validate

      ValidationErrors validate(T statement, Database database, SqlGeneratorChain<T> sqlGeneratorChain)
      Validate the data contained in the SqlStatement. If there are no errors, return an empty ValidationErrors object, not a null value. Liquibase will inspect the ValidationErrors result before attempting to call generateSql.

    • warn

      Warnings warn(T statementType, Database database, SqlGeneratorChain<T> sqlGeneratorChain)

    • generateSql

      Sql[] generateSql(T statement, Database database, SqlGeneratorChain<T> sqlGeneratorChain)
      Generate the actual Sql for the given statement and database.