Documentation
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Index ¶
Constants ¶
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Variables ¶
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Functions ¶
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Types ¶
type CallbackWriter ¶
type CallbackWriter struct {
DB *sql.DB
Delegate LDBWriter
Callbacks []LDBWriteCallback
ChangeBuffer *sqlite.SQLChangeBuffer
}
CallbackWriter is an LDBWriter that delegates to another writer and then, upon a successful write, executes N callbacks.
func (*CallbackWriter) ApplyDMLStatement ¶
func (w *CallbackWriter) ApplyDMLStatement(ctx context.Context, statement schema.DMLStatement) error
type ChangelogCallback ¶
type ChangelogCallback struct {
ChangelogWriter *changelog.ChangelogWriter
Seq int64
}
func (*ChangelogCallback) LDBWritten ¶
func (c *ChangelogCallback) LDBWritten(ctx context.Context, data LDBWriteMetadata)
type LDBWriteCallback ¶
type LDBWriteCallback interface {
LDBWritten(ctx context.Context, data LDBWriteMetadata)
}
type LDBWriteMetadata ¶
type LDBWriteMetadata struct {
DB *sql.DB
Statement schema.DMLStatement
Changes []sqlite.SQLiteWatchChange
}
LDBWriteMetadata contains the metadata about a statement that was written to the LDB.
type LDBWriter ¶
type LDBWriter interface {
ApplyDMLStatement(ctx context.Context, statement schema.DMLStatement) error
}
Statement to update the sequence tracker, ensuring that it doesn't go backwards without a round-trip to the DB and/or any race conditions. The statement is parameterized with the only one being the new sequence
type LDBWriterWithChangelog ¶
type LDBWriterWithChangelog struct {
LdbWriter LDBWriter
ChangelogWriter *changelog.ChangelogWriter
DB *sql.DB
ChangeBuffer *sqlite.SQLChangeBuffer
Seq int64
}
func (*LDBWriterWithChangelog) ApplyDMLStatement ¶
func (w *LDBWriterWithChangelog) ApplyDMLStatement(ctx context.Context, statement schema.DMLStatement) error
NOTE: How does the changelog work?
This is sort of the crux of how the changelog comes together. The Reflector sets a pre-update hook which populates a channel with any changes that happen in the LDB. These changes end up on a buffered channel. After each statement is executed, the pre-update hook will get called, filling in the channel. Once that ApplyDMLStatement returns, the DML statement is committed and the channel contains the contents of the update. Then this function takes over, extracts the keys from the update, and writes them to the changelogWriter.
This is pretty complex, but after enumerating about 8 different options, it ended up actually being the most simple. Other options involved not-so-great options like parsing SQL or maintaining triggers on every table.
type SqlLdbWriter ¶
ldbWriter applies statements to a SQL database
func (*SqlLdbWriter) ApplyDMLStatement ¶
func (writer *SqlLdbWriter) ApplyDMLStatement(_ context.Context, statement schema.DMLStatement) error
Applies a DML statement to the writer's db, updating the sequence tracking table in the same transaction
func (*SqlLdbWriter) Close ¶
func (writer *SqlLdbWriter) Close() error
Source Files