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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 CheckpointType ¶ added in v0.0.4
type CheckpointType string
CheckpointType see https://www.sqlite.org/pragma.html#pragma_wal_checkpoint
var ( Passive CheckpointType = "PASSIVE" Full CheckpointType = "FULL" Restart CheckpointType = "RESTART" Truncate CheckpointType = "TRUNCATE" )
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 PragmaWALResult ¶ added in v0.0.4
type PragmaWALResult struct {
// 0 indicates not busy, checkpoint was not blocked from completing. 1 is blocked
Busy int
// number of modified pages that have been written to the write-ahead log file per a checkpoint run
Log int
// number of pages in the write-ahead log file that have been successfully moved back into the database file at the conclusion of the checkpoint
Checkpointed int
// Type of checkpointing performed
Type CheckpointType
}
PragmaWALResult https://www.sqlite.org/pragma.html#pragma_wal_checkpoint
func (*PragmaWALResult) String ¶ added in v0.0.4
func (p *PragmaWALResult) String() string
type SqlLdbWriter ¶
type SqlLdbWriter struct {
Db *sql.DB
LedgerTx *sql.Tx
// uniquely identify this SqlWriter
Logger *events.Logger
ID string
}
ldbWriter applies statements to a SQL database
func (*SqlLdbWriter) ApplyDMLStatement ¶
func (w *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) Checkpoint ¶ added in v0.0.4
func (w *SqlLdbWriter) Checkpoint(checkpointingType CheckpointType) (*PragmaWALResult, error)
Checkpoint initiates a wal checkpoint, returning stats on the checkpoint's progress see https://www.sqlite.org/pragma.html#pragma_wal_checkpoint for more details requires write access
func (*SqlLdbWriter) Close ¶
func (w *SqlLdbWriter) Close() error
Source Files