Flow PHP

FileExtractor extends Extractor, Refreshable

Methods

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.
partitionSchema()  : Schema
prunes()  : bool
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.
source()  : Path
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

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>

yield from is allowed only as the whole body: it routes send() into the delegate, so the delegate sees Signal::STOP and this generator ends with it. A generator that does anything after delegating forwards with foreach + send().

$criteria is what the plan pushed into this read. A source returns only rows matching every one of $criteria->conjuncts; only a FileExtractor ever receives any. The limit and the path filter are hints: the plan still enforces the limit, and the predicate of every path filter is also one of the conjuncts or stays in a Filter node, so a source that reads or lists more is still correct. Batches built on another backend than $backend are adopted by the runtime. A record that cannot become a row is yielded as its CorruptedRecordException, in source order; the runtime routes or refuses it.

Parameters
$backend : Backend
$criteria : Criteria
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
bool

refresh()

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.

Tags
throws
InferredSchemaException

when no schema was declared and the source has no column to infer one from

SchemaNotDerivableException

when the source cannot describe what it will produce

Return values
Schema

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.

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
Statistics

withSchema()

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
Return values
static
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