yujun777 commented on code in PR #69851:
URL: https://github.com/apache/doris/pull/69851#discussion_r4419800603
##########
fe/fe-core/src/main/java/org/apache/doris/mtmv/ivm/IvmRewriteContext.java:
##########
@@ -163,11 +163,19 @@ public static IvmRewriteContext incrementalDryRun(MTMV
mtmv, Optional<IvmDryRunL
Collections.emptyMap());
}
- /** EXPLAIN REFRESH COMPLETE: only a plan is produced. */
+ /**
+ * EXPLAIN REFRESH COMPLETE: only a plan is produced, and it is the plan a
whole-MV COMPLETE
+ * refresh runs. That refresh reads every base table it does not partition
by with
+ * {@link StreamReadMode#RESET} (MTMVTask#executePartitionBasedRefresh
picks the mode: RESET for
+ * the first batch of a whole-MV refresh, SNAPSHOT afterwards), so a
context that left the mode
+ * empty would plan the normalized query over ordinary base scans -- a
different plan from the
+ * one the refresh executes. A refresh split into batches continues with
SNAPSHOT for the later
+ * ones, which one EXPLAIN statement cannot show.
+ */
public static IvmRewriteContext fullExplain(MTMV mtmv) {
return new IvmRewriteContext(Mode.FULL, Objects.requireNonNull(mtmv,
"mtmv can not be null"),
- null, false, ExecutionKind.EXPLAIN, Optional.empty(),
Collections.emptyMap(), Optional.empty(),
- Collections.emptyMap());
+ null, false, ExecutionKind.EXPLAIN, Optional.empty(),
Collections.emptyMap(),
+ Optional.of(StreamReadMode.RESET), Collections.emptyMap());
Review Comment:
Reworked in 3daed42, without carrying a reset scope. A complete refresh is
not one plan: it may be split into batches, whose later ones read non-PCT
tables at the stream offset (SNAPSHOT) and read tables the MV partitions by as
ordinary scans. One EXPLAIN statement stands for the refresh as a whole, so it
now shows the read the refresh starts with: `IvmFullRefreshMTMV` plans every
base table it reads through a stream with RESET under EXPLAIN, including the
tables the MV partitions by, over the partitions the plan selects. Resolving
the mapped reset scope would only be exact for a whole-MV refresh that fits in
one batch, while adding metadata work to the explain path, so the mode is
unified instead and the javadoc/PR state the contract.
`IvmFullRefreshMTMVTest#testExplainFullRefreshResetsATableTheMvPartitionsBy`
covers the partitioned-table path.
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