metamorphic: failure from 5/14

[nicktrav]

Found via a metamorphic test run (logs).

===== SEED =====
1652508047427439982
===== DIFF =====
/artifacts/meta/220514-060047.427/{standard-000,standard-008}
@@ -137,19 +137,19 @@
 db.RangeKeySet("dfdr", "dsmyui", "@1", "qmsu") // <nil> #137
 iter1.SeekGE("dsmyui@1", "") // [false] <nil> #138
 iter1.SetOptions("dfdr", "tlvnybcpi", 1 /* key types */, "" /* masking suffix */) // <nil> #139
 iter1.SeekPrefixGE("tlvnybcpi") // [false] <nil> #140
 batch2.Merge("tlvnybcpi", "qwzlmskgqfwxzoxmpt") // <nil> #141
-iter1.First() // [true,"dfdr",<no point>,["dfdr","dsmyui")=>{""="xhjdqkiufb","@1"="qmsu"}] <nil> #142
+iter1.First() // [true,"dfdr",<no point>,["dfdr","tlvnybcpi")=>{""="xhjdqkiufb"}] <nil> #142
 db.DeleteRange("tlvnybcpi", "vhicxainxj@1") // <nil> #143
 iter1.Prev("") // [false] <nil> #144
-iter1.SeekLT("vhicxainxj@1", "") // [true,"dsmyui",<no point>,["dsmyui","tlvnybcpi")=>{""="xhjdqkiufb"}] <nil> #145
-iter1.SeekGE("bjykm", "") // [true,"dfdr",<no point>,["dfdr","dsmyui")=>{""="xhjdqkiufb","@1"="qmsu"}] <nil> #146
+iter1.SeekLT("vhicxainxj@1", "") // [true,"dfdr",<no point>,["dfdr","tlvnybcpi")=>{""="xhjdqkiufb"}] <nil> #145
+iter1.SeekGE("bjykm", "") // [true,"dfdr",<no point>,["dfdr","tlvnybcpi")=>{""="xhjdqkiufb"}] <nil> #146
 db.Merge("dfdr", "rfgpzavquiyogmgxpe") // <nil> #147
-iter1.Next("vhicxainxj@1") // [valid,"dsmyui",<no point>,["dsmyui","tlvnybcpi")=>{""="xhjdqkiufb"}] <nil> #148
+iter1.Next("vhicxainxj@1") // [invalid] <nil> #148
 iter1.SetBounds("", "tlvnybcpi") // <nil> #149
-iter1.First() // [true,"dfdr",<no point>,["dfdr","dsmyui")=>{""="xhjdqkiufb","@1"="qmsu"}] <nil> #150
+iter1.First() // [true,"dfdr",<no point>,["dfdr","tlvnybcpi")=>{""="xhjdqkiufb"}] <nil> #150
 iter1.SetBounds("", "tlvnybcpi") // <nil> #151
 iter1.Prev("") // [false] <nil> #152
 iter1.SeekGE("tlvnybcpi", "") // [false] <nil> #153
 iter1.Close() // <nil> #154
 db.Ingest(batch2) // <nil> #155

SHA: b8c9a560bed5.

NOTE: I filled this in manually, as we didn't get an automated issue.

[nicktrav]

cc: @jbowens - similar to #1696. Possibly the same underlying issue, just want to track separately in case it's something different.

[jbowens]

Confirmed it's the same issue as #1696.

The problematic iterator is an iterator over an indexed batch.

iter1 = batch2.NewIter("", "", 0 /* key types */, "" /* masking suffix */) // <nil> #93

The batch receives a range key set over the span [dfdr, tlvnybcpi).

batch2.RangeKeySet("dfdr", "tlvnybcpi", "", "xhjdqkiufb") // <nil> #97

Later, a range key set is committed directly to the database.

db.RangeKeySet("dfdr", "dsmyui", "@1", "qmsu") // <nil> #137

Since this is committed after iter1 is opened, iter1 must not observe it. But in standard-000, it does:

iter1.First() // [true,"dfdr",<no point>,["dfdr","dsmyui")=>{""="xhjdqkiufb","@1"="qmsu"}] <nil> #142

This is because the batch's RANGEKEYSET again tickles the Span.Visible bug.