Support buffer forwarding in read_stream.c. In preparation for a follow-up change to the buffer manager, teach read_stream.c to manage buffers "forwarded" from one StartReadBuffers() call to the next after a short read. This involves a small amount of extra book-keeping, and opens the way for lower levels to split I/O operations without having to drop pins, as required for efficient handling of various edge cases.
Concretely, the "buffers" argument will change from an out parameter to an in/out parameter. Buffer queue elements must be initialized on first use and cleared after they're consumed, but forwarded buffers are left where they fall ahead of the current pending read in the queue, ready for use by the operation that continues where a short read left off. The stream also needs to count them for pin limit management and release them on reset/early end. Tested-by: Andres Freund <and...@anarazel.de> (earlier versions) Discussion: https://postgr.es/m/CA%2BhUKGK_%3D4CVmMHvsHjOVrK6t4F%3DLBpFzsrr3R%2BaJYN8kcTfWg%40mail.gmail.com Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/ed0b87caaca1eb3daa0f76f32499da7628286919 Modified Files -------------- src/backend/storage/aio/read_stream.c | 89 ++++++++++++++++++++++++++++++----- 1 file changed, 78 insertions(+), 11 deletions(-)
