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Fix wrong behavior of XREAD + after last entry of stream have been removed (#13632) 

Close #13628

This PR changes behavior of special `+` id of XREAD command. Now it uses
`streamLastValidID` to find last entry instead of `last_id` field of
stream object.
This PR adds test for the issue.

**Notes**

Initial idea to update `last_id` while executing XDEL seems to be wrong.
`last_id` is used to strore last generated id and not id of last entry.

---------

Co-authored-by: debing.sun <debing.sun@redis.com>
Co-authored-by: guybe7 <guy.benoish@redislabs.com>
This commit is contained in:
Denis Nevmerzhitskii 2025-02-25 07:40:24 +02:00 committed by GitHub
parent 985bf68f34
commit 33f03f6fc8
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GPG Key ID: B5690EEEBB952194
2 changed files with 33 additions and 7 deletions
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13
src/t_stream.c
View File

@ -2300,14 +2300,13 @@ void xreadCommand(client *c) {
"just return an empty result set.");
goto cleanup;
}
if (o) {
if (o && ((stream *)o->ptr)->length) {
stream *s = o->ptr;
ids[id_idx] = s->last_id;
if (streamDecrID(&ids[id_idx]) != C_OK) {
/* shouldn't happen */
addReplyError(c,"the stream last element ID is 0-0");
goto cleanup;
}
/* We need to get the last valid ID.
* It is impossible to use s->last_id because
* entry with s->last_id may have been removed. */
streamLastValidID(s, &ids[id_idx]);
streamDecrID(&ids[id_idx]);
} else {
ids[id_idx].ms = 0;
ids[id_idx].seq = 0;

27
tests/unit/type/stream.tcl
View File

@ -435,6 +435,17 @@ start_server {
# verify nil is still received when reading last entry
assert_equal [r XREAD STREAMS lestream +] {}
# case when stream created empty
# make sure the stream is not initialized
r DEL lestream
# create empty stream with XGROUP CREATE
r XGROUP CREATE lestream legroup $ MKSTREAM
# verify nil is received when reading last entry
assert_equal [r XREAD STREAMS lestream +] {}
}
test {XREAD last element blocking from empty stream} {
@ -510,6 +521,22 @@ start_server {
assert_equal $res {{lestream {{3-0 {k3 v3}}}}}
}
test "XREAD: read last element after XDEL (issue #13628)" {
# Should return actual last element after XDEL of current last element
# Add 2 entries to a stream and delete last one
r DEL stream
r XADD stream 1-0 f 1
r XADD stream 2-0 f 2
r XDEL stream 2-0
# Read last entry
set res [r XREAD STREAMS stream +]
# Verify the last entry was read
assert_equal $res {{stream {{1-0 {f 1}}}}}
}
test "XREAD: XADD + DEL should not awake client" {
set rd [redis_deferring_client]
r del s1