zy-kkk commented on code in PR #68453:
URL: https://github.com/apache/doris/pull/68453#discussion_r4114692193


##########
fe/fe-core/src/main/java/org/apache/doris/datasource/lance/LanceCatalogClient.java:
##########
@@ -235,68 +254,538 @@ public LanceTableMetadata loadBasicTableMetadata(String 
dbName, String tableName
     }
 
     public Schema loadTableSchema(String dbName, String tableName) {
-        return readTableSnapshot(dbName, tableName, Optional.empty(),
+        return readTableSnapshot(dbName, tableName, LanceRefSelector.latest(),
                 (dataset, access, metrics) -> metrics.measure(Stage.SCHEMA, 
dataset::getSchema));
     }
 
     public LanceTableMetadata loadTableMetadata(String dbName, String 
tableName,
             Optional<TableSnapshot> tableSnapshot) {
-        return loadQueryMetadata(dbName, tableName, tableSnapshot, 
LanceMetadataLoader.MetadataScope.WITH_INDEXES);
+        return loadTableMetadata(dbName, tableName, 
LanceRefSelector.snapshot(tableSnapshot));
+    }
+
+    public LanceTableMetadata loadTableMetadata(String dbName, String 
tableName, LanceRefSelector selector) {
+        return loadQueryMetadata(dbName, tableName, selector, 
LanceMetadataLoader.MetadataScope.WITH_INDEXES);
     }
 
     private LanceTableMetadata loadQueryMetadata(String dbName, String 
tableName,
             Optional<TableSnapshot> tableSnapshot, 
LanceMetadataLoader.MetadataScope mode) {
-        return readTableSnapshot(dbName, tableName, tableSnapshot,
+        return loadQueryMetadata(dbName, tableName, 
LanceRefSelector.snapshot(tableSnapshot), mode);
+    }
+
+    private LanceTableMetadata loadQueryMetadata(String dbName, String 
tableName,
+            LanceRefSelector selector, LanceMetadataLoader.MetadataScope mode) 
{
+        return readTableSnapshot(dbName, tableName, selector,
                 (dataset, access, metrics) -> 
LanceMetadataLoader.read(dataset, access, mode, metrics));
     }
 
-    /** Pins one resource generation, resolved table access, and the Dataset 
version for the whole read. */
-    private <T> T readTableSnapshot(String dbName, String tableName, 
Optional<TableSnapshot> tableSnapshot,
+    /**
+     * Pins one resource generation, resolved table access, and the Dataset 
version for the whole read.
+     *
+     * <p>The latest version of the main chain is opened once and every other 
selector is a
+     * checkout from that handle, so the SDK resolves the ref with the same 
commit handler
+     * (the namespace's, for a managed table). A tag is resolved first to the 
chain and version it
+     * points at, so a tag created on a branch selects that branch. The two 
shortcuts that skip the
+     * latest open are an explicit version on the main chain, and the latest 
version of a managed
+     * table. For a managed table, "latest" is always the newest version the 
namespace records,
+     * never the newest manifest in storage.
+     */
+    private <T> T readTableSnapshot(String dbName, String tableName, 
LanceRefSelector selector,
             SnapshotReader<T> reader) {
-        LanceTableAccess tableAccess = null;
+        try {
+            return readTableSnapshotOnce(dbName, tableName, selector, reader);
+        } catch (StaleTableAccessException e) {
+            // The cached access predates a location change the SDK has 
already seen. Read once
+            // more with a fresh access, so the FE plans and the BE reads the 
same location.
+            namespaceClient.invalidateTableAccess(dbName, tableName);
+            try {
+                return readTableSnapshotOnce(dbName, tableName, selector, 
reader);
+            } catch (StaleTableAccessException again) {
+                throw new RuntimeException("Lance namespace reported a 
different location for " + dbName + "."
+                        + tableName + " while it was being opened; retry the 
query");
+            }
+        }
+    }
+
+    private <T> T readTableSnapshotOnce(String dbName, String tableName, 
LanceRefSelector selector,
+            SnapshotReader<T> reader) {
+        ReadState state = new ReadState(selector, dbName + "." + tableName);
         LanceMetadataMetrics metrics = 
LanceMetadataMetrics.startMetadataRead();
         try {
             T result;
             try (BufferAllocator allocator = 
namespaceAllocator.newChildAllocator(
                     "lance-metadata-read", 0, namespaceAllocator.getLimit())) {
-                tableAccess = metrics.measure(Stage.TABLE_ACCESS,
+                state.access = metrics.measure(Stage.TABLE_ACCESS,
                         () -> namespaceClient.resolveTableAccess(dbName, 
tableName));
-                OptionalLong version = OptionalLong.empty();
-                if (tableSnapshot.isPresent()) {
-                    TableSnapshot snapshot = tableSnapshot.get();
-                    if (snapshot.getType() == 
TableSnapshot.VersionType.VERSION) {
-                        version = 
OptionalLong.of(LanceSnapshotResolver.parseVersion(snapshot.getValue()));
-                    } else {
-                        long timestamp = 
TimeUtils.timeStringToLong(snapshot.getValue(), TimeUtils.getTimeZone());
-                        if (timestamp < 0) {
-                            throw new IllegalArgumentException(
-                                    "Cannot parse Lance FOR TIME AS OF value 
'" + snapshot.getValue() + "'");
-                        }
-                        try (Dataset latest = openDataset(allocator, 
tableAccess, OptionalLong.empty(), metrics)) {
-                            version = 
OptionalLong.of(metrics.measure(Stage.VERSION_RESOLVE,
-                                    () -> 
LanceSnapshotResolver.getVersionAtOrBefore(latest, timestamp)));
-                        }
+                OptionalLong direct = directMainVersion(state, metrics);
+                if (direct.isPresent() || isLatestMain(selector)) {
+                    state.version = direct;
+                    try (Dataset dataset = openDataset(allocator, 
state.access, direct, metrics)) {
+                        result = reader.read(dataset, state.access, metrics);
+                    }
+                } else {
+                    OptionalLong mainVersion = 
state.access.isManagedVersioning()
+                            ? OptionalLong.of(recordedLatestVersion(state, 
Optional.empty(), metrics))
+                            : OptionalLong.empty();
+                    try (Dataset main = openDataset(allocator, state.access, 
mainVersion, metrics)) {
+                        result = readFromLatest(main, state, reader, metrics);
                     }
-                }
-                try (Dataset dataset = openDataset(allocator, tableAccess, 
version, metrics)) {
-                    result = reader.read(dataset, tableAccess, metrics);
                 }
             }
             metrics.succeeded();
             return result;
+        } catch (LanceUserFacingException e) {
+            throw new RuntimeException(e.getMessage(), e);
+        } catch (StaleTableAccessException e) {
+            throw e;
         } catch (Exception e) {
-            throw LanceErrorMessages.failure("Failed to load Lance table 
metadata for " + dbName + "." + tableName, e,
-                    tableAccess == null ? null : tableAccess.getDatasetUri(),
-                    tableAccess == null ? namespaceStorageOptions : 
tableAccess.getStorageOptions(), catalogSecrets);
+            LanceTableAccess access = state.access;
+            String uri = access == null ? null : access.getDatasetUri();
+            Map<String, String> options = access == null ? 
namespaceStorageOptions : access.getStorageOptions();
+            String what = state.displayName();
+            if (state.branch.isPresent() && !state.branchExists && 
isBranchNotFound(e, state.branch.get())) {
+                throw new RuntimeException("Lance branch '" + 
state.branch.get() + "' of " + state.tableName
+                        + state.selector.getTag().map(tag -> " (tag '" + tag + 
"')").orElse("")
+                        + " was not found" + (isNamespaceMiss(e, "table branch 
not found") ? " in the namespace" : ""),
+                        sanitizedCause(e, uri, options));
+            }
+            if (state.version.isPresent() && isVersionNotFound(e)) {
+                throw new RuntimeException("Lance version " + 
state.version.getAsLong() + " of " + what
+                        + state.selector.getTag().map(tag -> " (tag '" + tag + 
"')").orElse("")
+                        + " was not found" + (isNamespaceMiss(e, "table 
version not found") ? " in the namespace" : ""),
+                        sanitizedCause(e, uri, options));
+            }
+            String hint = access != null && access.isManagedVersioning() && 
isAccessDenied(e)
+                    ? " (reading a namespace-managed Lance table may need 
write access to finalize a staged manifest)"
+                    : "";
+            throw LanceErrorMessages.failure("Failed to load Lance table 
metadata for " + what + hint, e, uri, options,
+                    catalogSecrets);
         } finally {
             metrics.close();
         }
     }
 
+    /** What a read has resolved so far; the catch block reports errors 
against it. */
+    private static final class ReadState {
+        private final LanceRefSelector selector;
+        private final String tableName;
+        private LanceTableAccess access;
+        private Optional<String> branch;
+        /**
+         * Set once the branch is known to exist: the namespace recorded 
versions for it, or its
+         * latest version was checked out. Later failures are not reported as 
a missing branch.
+         */
+        private boolean branchExists;
+        private OptionalLong version = OptionalLong.empty();
+        /** The namespace's version list per chain ("" is main), fetched at 
most once per read. */
+        private final Map<String, List<TableVersion>> namespaceVersions = new 
HashMap<>();
+
+        private ReadState(LanceRefSelector selector, String tableName) {
+            this.selector = selector;
+            this.tableName = tableName;
+            this.branch = selector.getBranch();
+        }
+
+        private String displayName() {
+            return tableName + branch.map(name -> "@" + name).orElse("");
+        }
+    }
+
+    private static boolean isLatestMain(LanceRefSelector selector) {
+        return !selector.getTag().isPresent() && 
!selector.getBranch().isPresent()
+                && !selector.getSnapshot().isPresent();
+    }
+
+    /**
+     * The main-chain version a selector names without looking at the latest 
manifest: an explicit
+     * version, or the latest version of a managed table, which the namespace 
records.
+     */
+    private OptionalLong directMainVersion(ReadState state, 
LanceMetadataMetrics metrics) {
+        LanceRefSelector selector = state.selector;
+        if (selector.getTag().isPresent() || selector.getBranch().isPresent()) 
{
+            return OptionalLong.empty();
+        }
+        if (!selector.getSnapshot().isPresent()) {
+            return state.access.isManagedVersioning()
+                    ? OptionalLong.of(recordedLatestVersion(state, 
Optional.empty(), metrics))
+                    : OptionalLong.empty();
+        }
+        TableSnapshot snapshot = selector.getSnapshot().get();
+        return snapshot.getType() == TableSnapshot.VersionType.VERSION
+                ? 
OptionalLong.of(LanceSnapshotResolver.parseVersion(snapshot.getValue()))
+                : OptionalLong.empty();
+    }
+
+    /** Resolves the selector against the open latest main chain and reads the 
selected snapshot. */
+    private <T> T readFromLatest(Dataset main, ReadState state, 
SnapshotReader<T> reader, LanceMetadataMetrics metrics)
+            throws Exception {
+        LanceRefSelector selector = state.selector;
+        if (selector.getTag().isPresent()) {
+            // Only this tag's file is read, however many tags the table has. 
The SDK checks the tag
+            // out on the branch of the version it points at; for a managed 
table that is an
+            // explicit version the namespace resolves, never a storage 
fallback.
+            String tag = selector.getTag().get();
+            state.version = 
OptionalLong.of(metrics.measure(Stage.VERSION_RESOLVE, () -> tagVersion(main, 
tag, state)));
+            try (Dataset target = checkout(main, Ref.ofTag(tag), metrics)) {
+                state.branch = branchOf(target.uri(), 
state.access.getDatasetUri());
+                return reader.read(target, accessOf(target, state), metrics);
+            }
+        }
+        if (state.branch.isPresent()) {
+            String branch = state.branch.get();
+            // Check out the branch's latest version first even when a version 
is already known, so
+            // a missing branch and a missing version inside an existing 
branch are told apart.
+            Ref branchHead = Ref.ofBranch(branch);
+            if (state.access.isManagedVersioning()) {
+                branchHead = Ref.ofBranch(branch, recordedLatestVersion(state, 
Optional.of(branch), metrics));
+                state.branchExists = true;
+            }
+            try (Dataset latest = checkout(main, branchHead, metrics)) {
+                state.branchExists = true;
+                LanceTableAccess branchAccess = accessOf(latest, state);
+                if (!state.version.isPresent() && 
selector.getSnapshot().isPresent()) {
+                    state.version = resolveSnapshotVersion(latest, 
branchAccess, selector.getSnapshot().get(), state,
+                            metrics);
+                }
+                if (!state.version.isPresent()) {
+                    return reader.read(latest, branchAccess, metrics);
+                }
+                try (Dataset dataset = checkout(latest, Ref.ofBranch(branch, 
state.version.getAsLong()), metrics)) {
+                    return reader.read(dataset, branchAccess, metrics);
+                }
+            }
+        }
+        // FOR TIME AS OF on the main chain, resolved from manifest commit 
times.
+        state.version = resolveSnapshotVersion(main, state.access, 
selector.getSnapshot().get(), state, metrics);
+        try (Dataset dataset = checkout(main, 
Ref.ofMain(state.version.getAsLong()), metrics)) {
+            return reader.read(dataset, state.access, metrics);
+        }
+    }
+
+    private static long tagVersion(Dataset main, String tag, ReadState state) {
+        try {
+            return main.tags().getVersion(tag);
+        } catch (RuntimeException e) {
+            String rootMessage = ExceptionUtils.getRootCauseMessage(e);
+            if (rootMessage != null && rootMessage.contains("tag " + tag + " 
does not exist")) {
+                throw new LanceUserFacingException("Lance tag '" + tag + "' of 
" + state.tableName + " was not found");
+            }
+            throw e;
+        }
+    }
+
+    /**
+     * The branch a dataset checked out from the table root is on, from its 
root directory: the
+     * table root for main, {@code <root>/tree/<branch>} otherwise. Lance 
inserts the branch path
+     * before a URI's query string, so the query is compared apart. A URI that 
is neither is an
+     * error rather than main, which would hand the BE the wrong chain.
+     */
+    static Optional<String> branchOf(String checkedOutUri, String tableUri) {
+        String root = 
StringUtils.removeEnd(StringUtils.substringBefore(tableUri, "?"), "/");
+        String uri = 
StringUtils.removeEnd(StringUtils.substringBefore(checkedOutUri, "?"), "/");
+        if (uri.equals(root)) {
+            return Optional.empty();
+        }
+        String branchRoot = root + "/tree/";
+        if (!uri.startsWith(branchRoot) || uri.length() == 
branchRoot.length()) {
+            // The URIs may carry credentials in their query, so they stay out 
of the message.
+            throw new IllegalStateException("Cannot tell which branch a Lance 
tag was checked out on");
+        }
+        return Optional.of(uri.substring(branchRoot.length()));
+    }
+
+    /**
+     * The access for a dataset checked out from the table: the main chain 
keeps the table access,
+     * and a branch takes the directory the SDK checked out, which is what the 
BE opens by URI.
+     */
+    private static LanceTableAccess accessOf(Dataset dataset, ReadState state) 
{
+        return state.branch.isPresent() ? 
state.access.onBranch(state.branch.get(), dataset.uri()) : state.access;
+    }
+
+    /** A selector error whose message is user-facing as is, such as a tag 
that does not exist. */
+    private static final class LanceUserFacingException extends 
RuntimeException {
+        private LanceUserFacingException(String message) {
+            super(message);
+        }
+    }
+
+    /** The SDK opened a managed table at another location than the resolved 
access names. */
+    private static final class StaleTableAccessException extends 
RuntimeException {
+        private StaleTableAccessException() {
+            super("Lance table location changed since its access was 
resolved");
+        }
+    }
+
+    /**
+     * The newest version the namespace records for a managed chain. Doris 
asks for it itself:
+     * opening "latest" through the SDK falls back to the newest manifest in 
storage when the
+     * namespace records none, which would expose a version the namespace 
never published.
+     */
+    private long recordedLatestVersion(ReadState state, Optional<String> 
branch, LanceMetadataMetrics metrics) {
+        // A read that already listed the chain's versions reuses that list.
+        List<TableVersion> listed = 
state.namespaceVersions.get(branch.orElse(""));
+        OptionalLong latest = listed != null
+                ? 
listed.stream().map(TableVersion::getVersion).filter(Objects::nonNull)
+                        .mapToLong(Long::longValue).max()
+                : metrics.measure(Stage.VERSION_RESOLVE,
+                        () -> 
namespaceClient.latestManagedVersion(state.access, branch));
+        if (!latest.isPresent()) {
+            throw new LanceUserFacingException("Lance namespace lists no 
versions for " + state.tableName
+                    + branch.map(name -> "@" + name).orElse(""));
+        }
+        return latest.getAsLong();
+    }
+
+    private RuntimeException sanitizedCause(Throwable error, String uri, 
Map<String, String> options) {
+        return new RuntimeException(LanceErrorMessages.sanitize(error, uri, 
options, catalogSecrets));
+    }
+
+    /**
+     * Checks out a ref of an already open dataset. The SDK resolves the ref 
itself, from the
+     * dataset directory or, for a namespace-managed dataset, with its own 
namespace client.
+     */
+    private static Dataset checkout(Dataset dataset, Ref ref, 
LanceMetadataMetrics metrics) {
+        return metrics.measure(Stage.VERSION_RESOLVE, () -> 
dataset.checkout(ref));
+    }
+
+    /**
+     * Resolves a {@code FOR VERSION AS OF} / {@code FOR TIME AS OF} snapshot 
against the chain
+     * {@code latest} is checked out on: the main chain, or a branch when 
{@code access} is a
+     * branch access.
+     */
+    private OptionalLong resolveSnapshotVersion(Dataset latest, 
LanceTableAccess access, TableSnapshot snapshot,
+            ReadState state, LanceMetadataMetrics metrics) {
+        if (snapshot.getType() == TableSnapshot.VersionType.VERSION) {
+            return 
OptionalLong.of(LanceSnapshotResolver.parseVersion(snapshot.getValue()));
+        }
+        long timestamp = parseTimeTravelTimestamp(snapshot.getValue());
+        try {
+            return OptionalLong.of(resolveVersionAtOrBefore(latest, access, 
timestamp, snapshot.getValue(), state,
+                    metrics));
+        } catch (LanceSnapshotResolver.NoVersionAtOrBeforeException e) {
+            if (!access.getBranch().isPresent()) {
+                throw e;
+            }
+            // A branch's chain starts at the version it was created from and 
carries its own
+            // commit times, so an earlier timestamp has nothing to select on 
the branch.
+            throw new LanceUserFacingException("Lance branch '" + 
access.getBranch().get() + "' of "
+                    + state.tableName + " has no version at or before '" + 
snapshot.getValue()
+                    + "'; a branch only holds the versions from its creation 
on");
+        }
+    }
+
+    /**
+     * Whether a failed branch checkout means the branch does not exist. The 
SDK reports
+     * "branch <name> does not exist", a namespace "Table branch not found", 
or a missing manifest
+     * under the branch directory when nothing was ever committed there.
+     */
+    private static boolean isBranchNotFound(Throwable throwable, String 
branch) {
+        if (ExceptionUtils.indexOfType(throwable, 
TableBranchNotFoundException.class) >= 0) {
+            return true;
+        }
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        if (rootMessage == null) {
+            return false;
+        }
+        String lower = rootMessage.toLowerCase(Locale.ROOT);
+        String name = branch.toLowerCase(Locale.ROOT);
+        return lower.contains("table branch not found")
+                || lower.contains("branch " + name + " does not exist")
+                || (lower.contains("not found") && lower.contains("tree/" + 
name + "/"));
+    }
+
+    /**
+     * Whether a not-found came from the namespace rather than storage. The 
SDK surfaces a
+     * namespace error by its display text ("Table version not found: ..."), 
and the Java client
+     * by its exception type.
+     */
+    private static boolean isNamespaceMiss(Throwable throwable, String 
namespaceText) {
+        if (ExceptionUtils.indexOfType(throwable, 
TableVersionNotFoundException.class) >= 0
+                || ExceptionUtils.indexOfType(throwable, 
TableBranchNotFoundException.class) >= 0) {
+            return true;
+        }
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        return rootMessage != null && 
rootMessage.toLowerCase(Locale.ROOT).contains(namespaceText);
+    }
+
+    /** An HTTP 403 as the object stores report it, or an explicit 
access-denied error. */
+    private static final Pattern ACCESS_DENIED = Pattern.compile(
+            "accessdenied|access denied|permission 
denied|forbidden|(status|http|code)\\W{0,3}403\\b");
+
+    private static boolean isAccessDenied(Throwable throwable) {
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        return rootMessage != null && 
ACCESS_DENIED.matcher(rootMessage.toLowerCase(Locale.ROOT)).find();
+    }
+
+    /**
+     * Every version the namespace records for the chain {@code access} 
addresses, listed once per
+     * read. The whole list is needed: the storage fallback filters by it, and 
neither the order a
+     * namespace returns nor monotonic commit times can be relied on to stop 
early.
+     */
+    private List<TableVersion> namespaceVersions(ReadState state, 
LanceTableAccess access,
+            LanceMetadataMetrics metrics) {
+        return 
state.namespaceVersions.computeIfAbsent(access.getBranch().orElse(""), chain -> 
{
+            List<TableVersion> versions = 
metrics.measure(Stage.VERSION_RESOLVE,
+                    () -> namespaceClient.listManagedVersions(access));
+            if (versions.isEmpty()) {
+                throw new LanceUserFacingException("Lance namespace lists no 
versions for "
+                        + state.tableName + (chain.isEmpty() ? "" : "@" + 
chain));
+            }
+            return versions;
+        });
+    }
+
+    /**
+     * Resolves {@code FOR TIME AS OF} to a version on the chain {@code 
latest} is checked out on,
+     * from the commit times the manifests record, as Lance resolves {@code 
asof}. A managed table
+     * only selects among the versions its namespace records.
+     *
+     * <p>The version next to the selection must still exist: if the version 
after it, or with
+     * nothing listed at or before the time the one before the oldest listed, 
was removed by
+     * cleanup, the table's state at that time is unknown and the query fails 
instead of reading
+     * an older snapshot. A recorded version missing from the storage listing 
because its manifest
+     * is still staged is checked out there, which finalizes it and yields its 
commit time.
+     */
+    private long resolveVersionAtOrBefore(Dataset latest, LanceTableAccess 
access, long timestamp,
+            String requestedText, ReadState state, LanceMetadataMetrics 
metrics) {
+        NavigableSet<Long> recorded = access.isManagedVersioning()
+                ? namespaceVersions(state, access, 
metrics).stream().map(TableVersion::getVersion)
+                        
.filter(Objects::nonNull).collect(Collectors.toCollection(TreeSet::new))
+                : null;
+        long version = metrics.measure(Stage.VERSION_RESOLVE, () -> {
+            NavigableMap<Long, Version> listed = new TreeMap<>();
+            for (Version candidate : latest.listVersions()) {
+                if (recorded == null || recorded.contains(candidate.getId())) {
+                    listed.put(candidate.getId(), candidate);
+                }
+            }
+            long selected;
+            try {
+                selected = 
LanceSnapshotResolver.versionAtOrBefore(listed.values(), timestamp, 
requestedText);
+            } catch (LanceSnapshotResolver.NoVersionAtOrBeforeException e) {
+                if (recorded == null) {
+                    throw e;
+                }
+                // Recorded versions older than the oldest listed one may 
still be staged. Walking
+                // back, every version passed was committed after the time, so 
the first one at or
+                // before it is the answer.
+                Long older = listed.isEmpty() ? recorded.last() : 
recorded.lower(listed.firstKey());
+                while (older != null) {
+                    Version olderVersion = recordedVersion(latest, access, 
older);
+                    if (olderVersion == null) {
+                        throw historyRemoved(older, requestedText, state);
+                    }
+                    if (LanceSnapshotResolver.commitMillis(olderVersion) <= 
timestamp) {
+                        return older;
+                    }
+                    older = recorded.lower(older);
+                }
+                throw e;
+            }
+            // Lance numbers a chain's commits consecutively, so a storage 
chain is every number
+            // between the oldest and newest listed manifest; a managed chain 
is what is recorded.
+            Long next = nextVersion(selected, recorded, listed);
+            while (next != null) {
+                Version nextVersion = listed.containsKey(next) ? 
listed.get(next)
+                        : recorded == null ? null : recordedVersion(latest, 
access, next);
+                if (nextVersion == null) {
+                    throw historyRemoved(next, requestedText, state);
+                }
+                if (LanceSnapshotResolver.commitMillis(nextVersion) > 
timestamp) {
+                    break;
+                }
+                selected = next;

Review Comment:
   Confirmed, thanks. The gap walk assumed commit times grow with version 
numbers and overrode the comparator. Fixed in 41c6055c35f: selection now uses 
the `(commitMillis, version)` comparator throughout and assumes nothing about 
the order of commit times, so your first case selects v1.
   
   For removed versions it follows Iceberg's `TableMetadata.updateSnapshotLog`, 
which drops the snapshot log before a removed snapshot. A version removed by 
cleanup takes its commit time with it and could have been the answer, so only 
the versions newer than the newest removed one are candidates, and a time none 
of them covers fails instead of reading an older snapshot. For a managed table, 
every recorded version in that range that the storage listing lacks is checked 
out (which finalizes a staged manifest) to get its commit time, wherever it 
sits in the ID range, so your staged v3 case selects v3 and a staged version 
inside the listed range is found when no listed time qualifies.
   
   The selection moved into `LanceSnapshotResolver.versionAtOrBefore(listed, 
recorded, checkout, ...)`. `LanceSnapshotTest` covers your three cases and 
checks it against a direct reading of the rule on 20,000 random histories 
(repeated and backward commit times; staged, removed and unrecorded versions; 
storage and managed chains).



##########
fe/fe-core/src/main/java/org/apache/doris/datasource/lance/LanceCatalogClient.java:
##########
@@ -235,68 +254,538 @@ public LanceTableMetadata loadBasicTableMetadata(String 
dbName, String tableName
     }
 
     public Schema loadTableSchema(String dbName, String tableName) {
-        return readTableSnapshot(dbName, tableName, Optional.empty(),
+        return readTableSnapshot(dbName, tableName, LanceRefSelector.latest(),
                 (dataset, access, metrics) -> metrics.measure(Stage.SCHEMA, 
dataset::getSchema));
     }
 
     public LanceTableMetadata loadTableMetadata(String dbName, String 
tableName,
             Optional<TableSnapshot> tableSnapshot) {
-        return loadQueryMetadata(dbName, tableName, tableSnapshot, 
LanceMetadataLoader.MetadataScope.WITH_INDEXES);
+        return loadTableMetadata(dbName, tableName, 
LanceRefSelector.snapshot(tableSnapshot));
+    }
+
+    public LanceTableMetadata loadTableMetadata(String dbName, String 
tableName, LanceRefSelector selector) {
+        return loadQueryMetadata(dbName, tableName, selector, 
LanceMetadataLoader.MetadataScope.WITH_INDEXES);
     }
 
     private LanceTableMetadata loadQueryMetadata(String dbName, String 
tableName,
             Optional<TableSnapshot> tableSnapshot, 
LanceMetadataLoader.MetadataScope mode) {
-        return readTableSnapshot(dbName, tableName, tableSnapshot,
+        return loadQueryMetadata(dbName, tableName, 
LanceRefSelector.snapshot(tableSnapshot), mode);
+    }
+
+    private LanceTableMetadata loadQueryMetadata(String dbName, String 
tableName,
+            LanceRefSelector selector, LanceMetadataLoader.MetadataScope mode) 
{
+        return readTableSnapshot(dbName, tableName, selector,
                 (dataset, access, metrics) -> 
LanceMetadataLoader.read(dataset, access, mode, metrics));
     }
 
-    /** Pins one resource generation, resolved table access, and the Dataset 
version for the whole read. */
-    private <T> T readTableSnapshot(String dbName, String tableName, 
Optional<TableSnapshot> tableSnapshot,
+    /**
+     * Pins one resource generation, resolved table access, and the Dataset 
version for the whole read.
+     *
+     * <p>The latest version of the main chain is opened once and every other 
selector is a
+     * checkout from that handle, so the SDK resolves the ref with the same 
commit handler
+     * (the namespace's, for a managed table). A tag is resolved first to the 
chain and version it
+     * points at, so a tag created on a branch selects that branch. The two 
shortcuts that skip the
+     * latest open are an explicit version on the main chain, and the latest 
version of a managed
+     * table. For a managed table, "latest" is always the newest version the 
namespace records,
+     * never the newest manifest in storage.
+     */
+    private <T> T readTableSnapshot(String dbName, String tableName, 
LanceRefSelector selector,
             SnapshotReader<T> reader) {
-        LanceTableAccess tableAccess = null;
+        try {
+            return readTableSnapshotOnce(dbName, tableName, selector, reader);
+        } catch (StaleTableAccessException e) {
+            // The cached access predates a location change the SDK has 
already seen. Read once
+            // more with a fresh access, so the FE plans and the BE reads the 
same location.
+            namespaceClient.invalidateTableAccess(dbName, tableName);
+            try {
+                return readTableSnapshotOnce(dbName, tableName, selector, 
reader);
+            } catch (StaleTableAccessException again) {
+                throw new RuntimeException("Lance namespace reported a 
different location for " + dbName + "."
+                        + tableName + " while it was being opened; retry the 
query");
+            }
+        }
+    }
+
+    private <T> T readTableSnapshotOnce(String dbName, String tableName, 
LanceRefSelector selector,
+            SnapshotReader<T> reader) {
+        ReadState state = new ReadState(selector, dbName + "." + tableName);
         LanceMetadataMetrics metrics = 
LanceMetadataMetrics.startMetadataRead();
         try {
             T result;
             try (BufferAllocator allocator = 
namespaceAllocator.newChildAllocator(
                     "lance-metadata-read", 0, namespaceAllocator.getLimit())) {
-                tableAccess = metrics.measure(Stage.TABLE_ACCESS,
+                state.access = metrics.measure(Stage.TABLE_ACCESS,
                         () -> namespaceClient.resolveTableAccess(dbName, 
tableName));
-                OptionalLong version = OptionalLong.empty();
-                if (tableSnapshot.isPresent()) {
-                    TableSnapshot snapshot = tableSnapshot.get();
-                    if (snapshot.getType() == 
TableSnapshot.VersionType.VERSION) {
-                        version = 
OptionalLong.of(LanceSnapshotResolver.parseVersion(snapshot.getValue()));
-                    } else {
-                        long timestamp = 
TimeUtils.timeStringToLong(snapshot.getValue(), TimeUtils.getTimeZone());
-                        if (timestamp < 0) {
-                            throw new IllegalArgumentException(
-                                    "Cannot parse Lance FOR TIME AS OF value 
'" + snapshot.getValue() + "'");
-                        }
-                        try (Dataset latest = openDataset(allocator, 
tableAccess, OptionalLong.empty(), metrics)) {
-                            version = 
OptionalLong.of(metrics.measure(Stage.VERSION_RESOLVE,
-                                    () -> 
LanceSnapshotResolver.getVersionAtOrBefore(latest, timestamp)));
-                        }
+                OptionalLong direct = directMainVersion(state, metrics);
+                if (direct.isPresent() || isLatestMain(selector)) {
+                    state.version = direct;
+                    try (Dataset dataset = openDataset(allocator, 
state.access, direct, metrics)) {
+                        result = reader.read(dataset, state.access, metrics);
+                    }
+                } else {
+                    OptionalLong mainVersion = 
state.access.isManagedVersioning()
+                            ? OptionalLong.of(recordedLatestVersion(state, 
Optional.empty(), metrics))
+                            : OptionalLong.empty();
+                    try (Dataset main = openDataset(allocator, state.access, 
mainVersion, metrics)) {
+                        result = readFromLatest(main, state, reader, metrics);
                     }
-                }
-                try (Dataset dataset = openDataset(allocator, tableAccess, 
version, metrics)) {
-                    result = reader.read(dataset, tableAccess, metrics);
                 }
             }
             metrics.succeeded();
             return result;
+        } catch (LanceUserFacingException e) {
+            throw new RuntimeException(e.getMessage(), e);
+        } catch (StaleTableAccessException e) {
+            throw e;
         } catch (Exception e) {
-            throw LanceErrorMessages.failure("Failed to load Lance table 
metadata for " + dbName + "." + tableName, e,
-                    tableAccess == null ? null : tableAccess.getDatasetUri(),
-                    tableAccess == null ? namespaceStorageOptions : 
tableAccess.getStorageOptions(), catalogSecrets);
+            LanceTableAccess access = state.access;
+            String uri = access == null ? null : access.getDatasetUri();
+            Map<String, String> options = access == null ? 
namespaceStorageOptions : access.getStorageOptions();
+            String what = state.displayName();
+            if (state.branch.isPresent() && !state.branchExists && 
isBranchNotFound(e, state.branch.get())) {
+                throw new RuntimeException("Lance branch '" + 
state.branch.get() + "' of " + state.tableName
+                        + state.selector.getTag().map(tag -> " (tag '" + tag + 
"')").orElse("")
+                        + " was not found" + (isNamespaceMiss(e, "table branch 
not found") ? " in the namespace" : ""),
+                        sanitizedCause(e, uri, options));
+            }
+            if (state.version.isPresent() && isVersionNotFound(e)) {
+                throw new RuntimeException("Lance version " + 
state.version.getAsLong() + " of " + what
+                        + state.selector.getTag().map(tag -> " (tag '" + tag + 
"')").orElse("")
+                        + " was not found" + (isNamespaceMiss(e, "table 
version not found") ? " in the namespace" : ""),
+                        sanitizedCause(e, uri, options));
+            }
+            String hint = access != null && access.isManagedVersioning() && 
isAccessDenied(e)
+                    ? " (reading a namespace-managed Lance table may need 
write access to finalize a staged manifest)"
+                    : "";
+            throw LanceErrorMessages.failure("Failed to load Lance table 
metadata for " + what + hint, e, uri, options,
+                    catalogSecrets);
         } finally {
             metrics.close();
         }
     }
 
+    /** What a read has resolved so far; the catch block reports errors 
against it. */
+    private static final class ReadState {
+        private final LanceRefSelector selector;
+        private final String tableName;
+        private LanceTableAccess access;
+        private Optional<String> branch;
+        /**
+         * Set once the branch is known to exist: the namespace recorded 
versions for it, or its
+         * latest version was checked out. Later failures are not reported as 
a missing branch.
+         */
+        private boolean branchExists;
+        private OptionalLong version = OptionalLong.empty();
+        /** The namespace's version list per chain ("" is main), fetched at 
most once per read. */
+        private final Map<String, List<TableVersion>> namespaceVersions = new 
HashMap<>();
+
+        private ReadState(LanceRefSelector selector, String tableName) {
+            this.selector = selector;
+            this.tableName = tableName;
+            this.branch = selector.getBranch();
+        }
+
+        private String displayName() {
+            return tableName + branch.map(name -> "@" + name).orElse("");
+        }
+    }
+
+    private static boolean isLatestMain(LanceRefSelector selector) {
+        return !selector.getTag().isPresent() && 
!selector.getBranch().isPresent()
+                && !selector.getSnapshot().isPresent();
+    }
+
+    /**
+     * The main-chain version a selector names without looking at the latest 
manifest: an explicit
+     * version, or the latest version of a managed table, which the namespace 
records.
+     */
+    private OptionalLong directMainVersion(ReadState state, 
LanceMetadataMetrics metrics) {
+        LanceRefSelector selector = state.selector;
+        if (selector.getTag().isPresent() || selector.getBranch().isPresent()) 
{
+            return OptionalLong.empty();
+        }
+        if (!selector.getSnapshot().isPresent()) {
+            return state.access.isManagedVersioning()
+                    ? OptionalLong.of(recordedLatestVersion(state, 
Optional.empty(), metrics))
+                    : OptionalLong.empty();
+        }
+        TableSnapshot snapshot = selector.getSnapshot().get();
+        return snapshot.getType() == TableSnapshot.VersionType.VERSION
+                ? 
OptionalLong.of(LanceSnapshotResolver.parseVersion(snapshot.getValue()))
+                : OptionalLong.empty();
+    }
+
+    /** Resolves the selector against the open latest main chain and reads the 
selected snapshot. */
+    private <T> T readFromLatest(Dataset main, ReadState state, 
SnapshotReader<T> reader, LanceMetadataMetrics metrics)
+            throws Exception {
+        LanceRefSelector selector = state.selector;
+        if (selector.getTag().isPresent()) {
+            // Only this tag's file is read, however many tags the table has. 
The SDK checks the tag
+            // out on the branch of the version it points at; for a managed 
table that is an
+            // explicit version the namespace resolves, never a storage 
fallback.
+            String tag = selector.getTag().get();
+            state.version = 
OptionalLong.of(metrics.measure(Stage.VERSION_RESOLVE, () -> tagVersion(main, 
tag, state)));
+            try (Dataset target = checkout(main, Ref.ofTag(tag), metrics)) {
+                state.branch = branchOf(target.uri(), 
state.access.getDatasetUri());
+                return reader.read(target, accessOf(target, state), metrics);
+            }
+        }
+        if (state.branch.isPresent()) {
+            String branch = state.branch.get();
+            // Check out the branch's latest version first even when a version 
is already known, so
+            // a missing branch and a missing version inside an existing 
branch are told apart.
+            Ref branchHead = Ref.ofBranch(branch);
+            if (state.access.isManagedVersioning()) {
+                branchHead = Ref.ofBranch(branch, recordedLatestVersion(state, 
Optional.of(branch), metrics));
+                state.branchExists = true;
+            }
+            try (Dataset latest = checkout(main, branchHead, metrics)) {
+                state.branchExists = true;
+                LanceTableAccess branchAccess = accessOf(latest, state);
+                if (!state.version.isPresent() && 
selector.getSnapshot().isPresent()) {
+                    state.version = resolveSnapshotVersion(latest, 
branchAccess, selector.getSnapshot().get(), state,
+                            metrics);
+                }
+                if (!state.version.isPresent()) {
+                    return reader.read(latest, branchAccess, metrics);
+                }
+                try (Dataset dataset = checkout(latest, Ref.ofBranch(branch, 
state.version.getAsLong()), metrics)) {
+                    return reader.read(dataset, branchAccess, metrics);
+                }
+            }
+        }
+        // FOR TIME AS OF on the main chain, resolved from manifest commit 
times.
+        state.version = resolveSnapshotVersion(main, state.access, 
selector.getSnapshot().get(), state, metrics);
+        try (Dataset dataset = checkout(main, 
Ref.ofMain(state.version.getAsLong()), metrics)) {
+            return reader.read(dataset, state.access, metrics);
+        }
+    }
+
+    private static long tagVersion(Dataset main, String tag, ReadState state) {
+        try {
+            return main.tags().getVersion(tag);
+        } catch (RuntimeException e) {
+            String rootMessage = ExceptionUtils.getRootCauseMessage(e);
+            if (rootMessage != null && rootMessage.contains("tag " + tag + " 
does not exist")) {
+                throw new LanceUserFacingException("Lance tag '" + tag + "' of 
" + state.tableName + " was not found");
+            }
+            throw e;
+        }
+    }
+
+    /**
+     * The branch a dataset checked out from the table root is on, from its 
root directory: the
+     * table root for main, {@code <root>/tree/<branch>} otherwise. Lance 
inserts the branch path
+     * before a URI's query string, so the query is compared apart. A URI that 
is neither is an
+     * error rather than main, which would hand the BE the wrong chain.
+     */
+    static Optional<String> branchOf(String checkedOutUri, String tableUri) {
+        String root = 
StringUtils.removeEnd(StringUtils.substringBefore(tableUri, "?"), "/");
+        String uri = 
StringUtils.removeEnd(StringUtils.substringBefore(checkedOutUri, "?"), "/");
+        if (uri.equals(root)) {
+            return Optional.empty();
+        }
+        String branchRoot = root + "/tree/";
+        if (!uri.startsWith(branchRoot) || uri.length() == 
branchRoot.length()) {
+            // The URIs may carry credentials in their query, so they stay out 
of the message.
+            throw new IllegalStateException("Cannot tell which branch a Lance 
tag was checked out on");
+        }
+        return Optional.of(uri.substring(branchRoot.length()));
+    }
+
+    /**
+     * The access for a dataset checked out from the table: the main chain 
keeps the table access,
+     * and a branch takes the directory the SDK checked out, which is what the 
BE opens by URI.
+     */
+    private static LanceTableAccess accessOf(Dataset dataset, ReadState state) 
{
+        return state.branch.isPresent() ? 
state.access.onBranch(state.branch.get(), dataset.uri()) : state.access;
+    }
+
+    /** A selector error whose message is user-facing as is, such as a tag 
that does not exist. */
+    private static final class LanceUserFacingException extends 
RuntimeException {
+        private LanceUserFacingException(String message) {
+            super(message);
+        }
+    }
+
+    /** The SDK opened a managed table at another location than the resolved 
access names. */
+    private static final class StaleTableAccessException extends 
RuntimeException {
+        private StaleTableAccessException() {
+            super("Lance table location changed since its access was 
resolved");
+        }
+    }
+
+    /**
+     * The newest version the namespace records for a managed chain. Doris 
asks for it itself:
+     * opening "latest" through the SDK falls back to the newest manifest in 
storage when the
+     * namespace records none, which would expose a version the namespace 
never published.
+     */
+    private long recordedLatestVersion(ReadState state, Optional<String> 
branch, LanceMetadataMetrics metrics) {
+        // A read that already listed the chain's versions reuses that list.
+        List<TableVersion> listed = 
state.namespaceVersions.get(branch.orElse(""));
+        OptionalLong latest = listed != null
+                ? 
listed.stream().map(TableVersion::getVersion).filter(Objects::nonNull)
+                        .mapToLong(Long::longValue).max()
+                : metrics.measure(Stage.VERSION_RESOLVE,
+                        () -> 
namespaceClient.latestManagedVersion(state.access, branch));
+        if (!latest.isPresent()) {
+            throw new LanceUserFacingException("Lance namespace lists no 
versions for " + state.tableName
+                    + branch.map(name -> "@" + name).orElse(""));
+        }
+        return latest.getAsLong();
+    }
+
+    private RuntimeException sanitizedCause(Throwable error, String uri, 
Map<String, String> options) {
+        return new RuntimeException(LanceErrorMessages.sanitize(error, uri, 
options, catalogSecrets));
+    }
+
+    /**
+     * Checks out a ref of an already open dataset. The SDK resolves the ref 
itself, from the
+     * dataset directory or, for a namespace-managed dataset, with its own 
namespace client.
+     */
+    private static Dataset checkout(Dataset dataset, Ref ref, 
LanceMetadataMetrics metrics) {
+        return metrics.measure(Stage.VERSION_RESOLVE, () -> 
dataset.checkout(ref));
+    }
+
+    /**
+     * Resolves a {@code FOR VERSION AS OF} / {@code FOR TIME AS OF} snapshot 
against the chain
+     * {@code latest} is checked out on: the main chain, or a branch when 
{@code access} is a
+     * branch access.
+     */
+    private OptionalLong resolveSnapshotVersion(Dataset latest, 
LanceTableAccess access, TableSnapshot snapshot,
+            ReadState state, LanceMetadataMetrics metrics) {
+        if (snapshot.getType() == TableSnapshot.VersionType.VERSION) {
+            return 
OptionalLong.of(LanceSnapshotResolver.parseVersion(snapshot.getValue()));
+        }
+        long timestamp = parseTimeTravelTimestamp(snapshot.getValue());
+        try {
+            return OptionalLong.of(resolveVersionAtOrBefore(latest, access, 
timestamp, snapshot.getValue(), state,
+                    metrics));
+        } catch (LanceSnapshotResolver.NoVersionAtOrBeforeException e) {
+            if (!access.getBranch().isPresent()) {
+                throw e;
+            }
+            // A branch's chain starts at the version it was created from and 
carries its own
+            // commit times, so an earlier timestamp has nothing to select on 
the branch.
+            throw new LanceUserFacingException("Lance branch '" + 
access.getBranch().get() + "' of "
+                    + state.tableName + " has no version at or before '" + 
snapshot.getValue()
+                    + "'; a branch only holds the versions from its creation 
on");
+        }
+    }
+
+    /**
+     * Whether a failed branch checkout means the branch does not exist. The 
SDK reports
+     * "branch <name> does not exist", a namespace "Table branch not found", 
or a missing manifest
+     * under the branch directory when nothing was ever committed there.
+     */
+    private static boolean isBranchNotFound(Throwable throwable, String 
branch) {
+        if (ExceptionUtils.indexOfType(throwable, 
TableBranchNotFoundException.class) >= 0) {
+            return true;
+        }
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        if (rootMessage == null) {
+            return false;
+        }
+        String lower = rootMessage.toLowerCase(Locale.ROOT);
+        String name = branch.toLowerCase(Locale.ROOT);
+        return lower.contains("table branch not found")
+                || lower.contains("branch " + name + " does not exist")
+                || (lower.contains("not found") && lower.contains("tree/" + 
name + "/"));
+    }
+
+    /**
+     * Whether a not-found came from the namespace rather than storage. The 
SDK surfaces a
+     * namespace error by its display text ("Table version not found: ..."), 
and the Java client
+     * by its exception type.
+     */
+    private static boolean isNamespaceMiss(Throwable throwable, String 
namespaceText) {
+        if (ExceptionUtils.indexOfType(throwable, 
TableVersionNotFoundException.class) >= 0
+                || ExceptionUtils.indexOfType(throwable, 
TableBranchNotFoundException.class) >= 0) {
+            return true;
+        }
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        return rootMessage != null && 
rootMessage.toLowerCase(Locale.ROOT).contains(namespaceText);
+    }
+
+    /** An HTTP 403 as the object stores report it, or an explicit 
access-denied error. */
+    private static final Pattern ACCESS_DENIED = Pattern.compile(
+            "accessdenied|access denied|permission 
denied|forbidden|(status|http|code)\\W{0,3}403\\b");
+
+    private static boolean isAccessDenied(Throwable throwable) {
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        return rootMessage != null && 
ACCESS_DENIED.matcher(rootMessage.toLowerCase(Locale.ROOT)).find();
+    }
+
+    /**
+     * Every version the namespace records for the chain {@code access} 
addresses, listed once per
+     * read. The whole list is needed: the storage fallback filters by it, and 
neither the order a
+     * namespace returns nor monotonic commit times can be relied on to stop 
early.
+     */
+    private List<TableVersion> namespaceVersions(ReadState state, 
LanceTableAccess access,
+            LanceMetadataMetrics metrics) {
+        return 
state.namespaceVersions.computeIfAbsent(access.getBranch().orElse(""), chain -> 
{
+            List<TableVersion> versions = 
metrics.measure(Stage.VERSION_RESOLVE,
+                    () -> namespaceClient.listManagedVersions(access));
+            if (versions.isEmpty()) {
+                throw new LanceUserFacingException("Lance namespace lists no 
versions for "
+                        + state.tableName + (chain.isEmpty() ? "" : "@" + 
chain));
+            }
+            return versions;
+        });
+    }
+
+    /**
+     * Resolves {@code FOR TIME AS OF} to a version on the chain {@code 
latest} is checked out on,
+     * from the commit times the manifests record, as Lance resolves {@code 
asof}. A managed table
+     * only selects among the versions its namespace records.
+     *
+     * <p>The version next to the selection must still exist: if the version 
after it, or with
+     * nothing listed at or before the time the one before the oldest listed, 
was removed by
+     * cleanup, the table's state at that time is unknown and the query fails 
instead of reading
+     * an older snapshot. A recorded version missing from the storage listing 
because its manifest
+     * is still staged is checked out there, which finalizes it and yields its 
commit time.
+     */
+    private long resolveVersionAtOrBefore(Dataset latest, LanceTableAccess 
access, long timestamp,
+            String requestedText, ReadState state, LanceMetadataMetrics 
metrics) {
+        NavigableSet<Long> recorded = access.isManagedVersioning()
+                ? namespaceVersions(state, access, 
metrics).stream().map(TableVersion::getVersion)
+                        
.filter(Objects::nonNull).collect(Collectors.toCollection(TreeSet::new))
+                : null;
+        long version = metrics.measure(Stage.VERSION_RESOLVE, () -> {
+            NavigableMap<Long, Version> listed = new TreeMap<>();
+            for (Version candidate : latest.listVersions()) {
+                if (recorded == null || recorded.contains(candidate.getId())) {
+                    listed.put(candidate.getId(), candidate);
+                }
+            }
+            long selected;
+            try {
+                selected = 
LanceSnapshotResolver.versionAtOrBefore(listed.values(), timestamp, 
requestedText);
+            } catch (LanceSnapshotResolver.NoVersionAtOrBeforeException e) {
+                if (recorded == null) {
+                    throw e;
+                }
+                // Recorded versions older than the oldest listed one may 
still be staged. Walking
+                // back, every version passed was committed after the time, so 
the first one at or
+                // before it is the answer.
+                Long older = listed.isEmpty() ? recorded.last() : 
recorded.lower(listed.firstKey());
+                while (older != null) {
+                    Version olderVersion = recordedVersion(latest, access, 
older);
+                    if (olderVersion == null) {
+                        throw historyRemoved(older, requestedText, state);
+                    }
+                    if (LanceSnapshotResolver.commitMillis(olderVersion) <= 
timestamp) {
+                        return older;
+                    }
+                    older = recorded.lower(older);
+                }
+                throw e;
+            }
+            // Lance numbers a chain's commits consecutively, so a storage 
chain is every number
+            // between the oldest and newest listed manifest; a managed chain 
is what is recorded.
+            Long next = nextVersion(selected, recorded, listed);
+            while (next != null) {
+                Version nextVersion = listed.containsKey(next) ? 
listed.get(next)
+                        : recorded == null ? null : recordedVersion(latest, 
access, next);
+                if (nextVersion == null) {
+                    throw historyRemoved(next, requestedText, state);
+                }
+                if (LanceSnapshotResolver.commitMillis(nextVersion) > 
timestamp) {
+                    break;
+                }
+                selected = next;
+                next = nextVersion(next, recorded, listed);
+            }
+            return selected;
+        });
+        LOG.debug("Resolved Lance FOR TIME AS OF '{}' to version {} from 
manifest commit times", requestedText,
+                version);
+        return version;
+    }
+
+    private static Long nextVersion(long version, NavigableSet<Long> recorded, 
NavigableMap<Long, Version> listed) {
+        if (recorded != null) {
+            return recorded.higher(version);
+        }
+        return version < listed.lastKey() ? version + 1 : null;
+    }
+
+    /**
+     * A namespace-recorded version checked out through the namespace, or null 
if it is gone. A
+     * still-staged manifest is finalized by the checkout.
+     */
+    private static Version recordedVersion(Dataset latest, LanceTableAccess 
access, long version) {
+        Ref ref = access.getBranch().map(name -> Ref.ofBranch(name, 
version)).orElseGet(() -> Ref.ofMain(version));
+        try (Dataset recorded = latest.checkout(ref)) {
+            return recorded.getVersion();
+        } catch (Exception e) {
+            // Also the IOException the JNI raises for a missing manifest.
+            if (!isVersionNotFound(e)) {
+                throw e;
+            }
+            return null;
+        }
+    }
+
+    private static LanceUserFacingException historyRemoved(long version, 
String requestedText, ReadState state) {
+        return new LanceUserFacingException("Lance cannot resolve FOR TIME AS 
OF '" + requestedText + "' on "
+                + state.displayName() + ": version " + version + ", which may 
hold the state at that time,"
+                + " no longer exists");
+    }
+
+    /**
+     * Parses a {@code FOR TIME AS OF} value in the session time zone. Second 
and millisecond
+     * precision are accepted; commit times are compared at millisecond 
precision, the precision a
+     * namespace reports them in, so a timestamp in the millisecond a commit 
lands in selects it.
+     */
+    private static long parseTimeTravelTimestamp(String value) {
+        long timestamp = TimeUtils.timeStringToLong(value, 
TimeUtils.getTimeZone());
+        if (timestamp < 0) {
+            timestamp = TimeUtils.msTimeStringToLong(value, 
TimeUtils.getTimeZone());
+        }
+        if (timestamp < 0) {
+            throw new IllegalArgumentException("Cannot parse Lance FOR TIME AS 
OF value '" + value
+                    + "', expected 'yyyy-MM-dd HH:mm:ss' or 'yyyy-MM-dd 
HH:mm:ss.SSS'");
+        }
+        return timestamp;
+    }
+
+    /**
+     * Whether a failed open of an explicitly requested version means that 
version does not exist.
+     * A namespace reports it through {@link TableVersionNotFoundException}. 
The storage reader
+     * reports it as a missing manifest under {@code _versions/} or as Lance's 
own version-not-found
+     * error; a missing dataset or an unreachable store fails differently and 
keeps its message.
+     */
+    private static boolean isVersionNotFound(Throwable throwable) {
+        if (ExceptionUtils.indexOfType(throwable, 
TableVersionNotFoundException.class) >= 0) {
+            return true;
+        }
+        String rootMessage = ExceptionUtils.getRootCauseMessage(throwable);
+        if (rootMessage == null) {
+            return false;
+        }
+        String lower = rootMessage.toLowerCase(Locale.ROOT);
+        return lower.contains("version not found")
+                || (lower.contains("not found") && 
lower.contains("_versions/"));
+    }
+
     private Dataset openDataset(BufferAllocator allocator, LanceTableAccess 
access, OptionalLong version,
             LanceMetadataMetrics metrics) {
+        ReadOptions readOptions = 
LanceReadOptions.forSharedSession(access.getSdkStorageOptions(), version, 
session);
+        if (access.isManagedVersioning()) {
+            // The SDK re-describes the table and opens the location the 
namespace returns, so a
+            // namespace that returns a relative location cannot be read in 
this mode. The BE
+            // opens the access's location, so both must still agree after 
that second describe.
+            Dataset dataset = metrics.measure(Stage.DATASET_OPEN,
+                    () -> namespaceClient.openManagedDataset(allocator, 
access, readOptions, session));
+            if (!StringUtils.removeEnd(dataset.uri(), 
"/").equals(StringUtils.removeEnd(access.getDatasetUri(), "/"))) {

Review Comment:
   Confirmed, thanks. Fixed in 41c6055c35f: after a managed open, the access 
handed to the BE is rebuilt from what the SDK opened with. 
`Dataset.getInitialStorageOptions()` returns the options the SDK opened with, 
which are the ones Doris passed with the vended options of the SDK's describe 
put on top, so every entry that differs from what Doris passed came from that 
describe. `LanceNamespaceClient.accessOpenedBySdk` rebuilds the access from 
those vended options and the URI the SDK opened, with the same normalization as 
the first describe, so the BE reads the same location with the same 
configuration; a namespace that vends fresh credentials on every describe just 
passes the SDK's to the BE.
   
   If the SDK did not open with exactly the rebuilt access's options, for 
example when the namespace starts vending an option under another spelling 
(`endpoint` next to the catalog's `aws_endpoint`) or moves the table to another 
store, the dataset is opened once more with the rebuilt options, and a second 
mismatch fails with a retry message. That replaces the relocation 
compare-and-retry from the previous round.
   
   `LanceSdkOpenedAccessTest` runs without the native library, so it runs in 
CI: a same-URI `aws_endpoint` change from storage A to B with rotated 
credentials, an alias spelling, an endpoint leaving plain HTTP, a describe that 
vends nothing or drops a key, relocation within a store and to another store. 
`LanceManagedVersioningTest.testBeReadsWithTheOptionsTheSdkOpenedWith` 
exercises it through the real SDK against a namespace stub that vends a new 
value on every describe (that class needs the Arrow C Data JNI library, so it 
runs locally only).



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