Package dev.frostlake.executor.expressions

Class RowOrdinal

java.lang.Object
dev.frostlake.executor.expressions.RowOrdinal
public final class RowOrdinal extends Object
Which row, counting from 0, the operator is currently evaluating expressions for — what the SEQ1 / SEQ2 / SEQ4 / SEQ8 family reads.

The ordinal belongs to the ROW, not to the call. Measured live, two SEQ4() calls in one row return the SAME number (SEQ4() + SEQ4() yields 0, 2, 4, 6 — not 0+1, 2+3), and a SEQ4() in a subquery agrees with one in the block above it. A counter incremented inside the function — the shape RANDOM and UUID_STRING use — would number the CALLS and get every one of those wrong, which is why the count lives out here and the function only reads it.

Set once per row by the operator that iterates rows, so all of a row's expressions see one value. That also places the count where Snowflake places it: an operator numbers the rows it is HANDED, so a WHERE that ran earlier in the pipeline has already removed rows and the projection numbers the survivors from 0 — live, SELECT x, SEQ4() FROM t WHERE x > 4 over 1..8 returns 5|0 6|1 7|2 8|3.

Scoped to the thread, like ExpressionSource and the statement clock, because a session's statements run on the caller's thread. Unset means row 0: a SELECT with no FROM never reaches an operator at all, and live answers SEQ4() there with 0.

  • Method Summary

    Modifier and Type
    Method
    Description
    static Long
    begin(long ordinal)
    Note the row about to be evaluated, returning whatever ordinal it displaced so a nested evaluation — a scalar subquery runs its own operators mid-row — can put it back.
    static long
    current()
    The current row's 0-based ordinal, or 0 when nothing has set one.
    static void
    end(Long previous)
    Put back whatever begin(long) displaced; null clears.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • begin

      public static Long begin(long ordinal)
      Note the row about to be evaluated, returning whatever ordinal it displaced so a nested evaluation — a scalar subquery runs its own operators mid-row — can put it back.

    • end

      public static void end(Long previous)
      Put back whatever begin(long) displaced; null clears.

    • current

      public static long current()
      The current row's 0-based ordinal, or 0 when nothing has set one.