Package io.github.flink.gcp.connector.spanner.source

Class SpannerReadOperation

java.lang.Object
io.github.flink.gcp.connector.spanner.source.SpannerReadOperation
All Implemented Interfaces:
Serializable
@Public public final class SpannerReadOperation extends Object implements Serializable
What the batch source reads: either a query, or a table with its columns and key set, optionally through an index. 

 SpannerReadOperation.query(Statement.of("SELECT id, name FROM singers"));
 SpannerReadOperation.read("singers", KeySet.all(), Arrays.asList("id", "name"));
 SpannerReadOperation.readUsingIndex(
         "singers", "singers_by_name", KeySet.all(), Arrays.asList("id", "name"));

The two shapes are exclusive because Spanner's own API makes them so — partitionQuery takes a statement and partitionRead takes a table — and holding them in one value object is what lets the builder take a single option rather than five that only make sense in two combinations.

Lineage reports the configured base table for explicit reads, including index reads. An index is only an access path. Query dependencies are unknown: the source neither parses SQL nor submits it to discover lineage, and returns an empty dataset list for a query.

Not every query can be read this way. Spanner partitions a query only when its execution plan begins with a distributed union — in practice a scan of one table, with predicates and projections but no aggregate, no ORDER BY and no LIMIT. A query that is not root-partitionable is refused by the service when the source plans, with a message naming the reason, and the source fails rather than silently reading it on one subtask.

See Also:

  • Method Details

    • query

      public static SpannerReadOperation query(com.google.cloud.spanner.Statement statement)
      Reads the rows a query returns.
      Parameters:
      statement - the query, with its parameter bindings if it has any
      Returns:
      the read operation

    • read

      public static SpannerReadOperation read(String table, com.google.cloud.spanner.KeySet keys, List<String> columns)
      Reads columns of a table over a key set.
      Parameters:
      table - the table name
      keys - the keys and key ranges to read; KeySet.all() for the whole table
      columns - the columns to return, at least one
      Returns:
      the read operation

    • readUsingIndex

      public static SpannerReadOperation readUsingIndex(String table, String index, com.google.cloud.spanner.KeySet keys, List<String> columns)
      Reads columns of a table over a key set, through a secondary index.

      The key set is interpreted in the index's key space, not the table's, and a read can return only index key columns, base-table primary-key columns, and columns included with STORING or INCLUDE.

      Parameters:
      table - the table name
      index - the index name
      keys - the keys and key ranges to read, in the index's key space
      columns - the columns to return, at least one
      Returns:
      the read operation

    • isQuery

      public boolean isQuery()
      Returns whether this is a query rather than a table read.
      Returns:
      whether this operation is a query

    • getStatement

      @Nullable public com.google.cloud.spanner.Statement getStatement()
      Returns the query, when this is one.
      Returns:
      the query, or null when this is a table read

    • getTable

      @Nullable public String getTable()
      Returns the table to read, when this is a table read.
      Returns:
      the table name, or null when this is a query

    • getIndex

      @Nullable public String getIndex()
      Returns the index to read through.
      Returns:
      the index name, or null for a read of the table itself or for a query

    • getKeys

      @Nullable public com.google.cloud.spanner.KeySet getKeys()
      Returns the keys to read, when this is a table read.
      Returns:
      the key set, or null when this is a query

    • getColumns

      @Nullable public List<String> getColumns()
      Returns the columns to return, when this is a table read.
      Returns:
      the columns, or null when this is a query

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object