ChainExtractor implements Extractor, Refreshable
Interfaces
Methods
- __construct() : mixed
- extract() : Generator<Signal|null, void>
- Yields rows in batches. When the source is a BatchableExtractor a batch holds between 0 and that extractor's own batchSize() rows; the size is chosen by the extractor and MAY vary between batches. Consumers must not assume a minimum size, a constant size, or a non-empty batch.
- isRepeatable() : bool
- True when extract() can run more than once and yield the same rows each time, so a build-time pass may read the source before the run without consuming it. A one-shot stream returns false; a wrapper answers for what it reads.
- refresh() : void
- Drops the listing and everything derived from it, so the next run lists the source again. A run calls it when it ends; a plan that does not run (explain(), schema()) keeps what it listed for the run that follows.
- schema() : Schema
- Answers before extract() runs, so every batch it yields carries this shape. Takes no FlowContext: a source that needs the pipeline's context to describe itself has not moved the answer to bind time.
- statistics() : Statistics
- What the source knows about the data before a single row is read: how many rows, how many bytes. A source that knows nothing returns `new Statistics()`. Describes the source with NO pushdown applied - a limit or a partition filter the plan pushed is the plan's to account for.
- withSchema() : static
- Declares the shape every yielded batch must carry. A source that describes itself uses this instead of its own description, and values are cast to fit.
Methods
__construct()
public
__construct(Extractor ...$extractors) : mixed
Parameters
- $extractors : Extractor
extract()
Yields rows in batches. When the source is a BatchableExtractor a batch holds between 0 and that extractor's own batchSize() rows; the size is chosen by the extractor and MAY vary between batches. Consumers must not assume a minimum size, a constant size, or a non-empty batch.
public
extract(Backend $backend, Criteria $criteria) : Generator<Signal|null, void>
Parameters
Return values
Generator<Signal|null, void>isRepeatable()
True when extract() can run more than once and yield the same rows each time, so a build-time pass may read the source before the run without consuming it. A one-shot stream returns false; a wrapper answers for what it reads.
public
isRepeatable() : bool
Return values
boolrefresh()
Drops the listing and everything derived from it, so the next run lists the source again. A run calls it when it ends; a plan that does not run (explain(), schema()) keeps what it listed for the run that follows.
public
refresh() : void
schema()
Answers before extract() runs, so every batch it yields carries this shape. Takes no FlowContext: a source that needs the pipeline's context to describe itself has not moved the answer to bind time.
public
schema() : Schema
Called once per RUN - every run plans afresh - so it MUST be idempotent and cheap on repeat: memoise what it sniffs, as CSVExtractor and ArrayExtractor do.
Return values
Schemastatistics()
What the source knows about the data before a single row is read: how many rows, how many bytes. A source that knows nothing returns `new Statistics()`. Describes the source with NO pushdown applied - a limit or a partition filter the plan pushed is the plan's to account for.
public
statistics() : Statistics
Called AT MOST ONCE per run, and only when something needs the answer - so it must be lazy, never computed in the constructor - and it MUST be idempotent and cheap on repeat: memoise what it reads, the way schema() does.
A file source may only spend what the run already spends: it may complete a listing it must produce anyway and read metadata from the files schema() already opens, and it may extrapolate from those. It must not open an extra file or make an extra remote call. A database source may ask the planner for an estimate (EXPLAIN without ANALYZE), never run the query.
Return values
StatisticswithSchema()
Declares the shape every yielded batch must carry. A source that describes itself uses this instead of its own description, and values are cast to fit.
public
withSchema(Schema $schema) : static
Parameters
- $schema : Schema