MvccUtil.java

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package org.apache.doris.datasource.mvcc;

import org.apache.doris.analysis.TableScanParams;
import org.apache.doris.analysis.TableSnapshot;
import org.apache.doris.catalog.TableIf;
import org.apache.doris.nereids.StatementContext;
import org.apache.doris.qe.ConnectContext;

import java.util.Optional;

public class MvccUtil {
    /**
     * get Snapshot From StatementContext
     *
     * @param tableIf
     * @return MvccSnapshot
     */
    public static Optional<MvccSnapshot> getSnapshotFromContext(TableIf tableIf) {
        ConnectContext connectContext = ConnectContext.get();
        if (connectContext == null) {
            return Optional.empty();
        }
        StatementContext statementContext = connectContext.getStatementContext();
        if (statementContext == null) {
            return Optional.empty();
        }
        return statementContext.getSnapshot(tableIf);
    }

    /**
     * Get the version-aware Snapshot from the StatementContext: resolves the snapshot pinned for the SAME
     * table reference (same {@code @branch}/{@code @tag}/FOR-TIME selector) the scan carries, so a statement
     * mixing main and {@code @branch} of one table reads each at its own snapshot. The version-blind
     * {@link #getSnapshotFromContext(TableIf)} cannot disambiguate once more than one snapshot is pinned.
     *
     * @param tableIf       tableIf
     * @param tableSnapshot the reference's FOR VERSION/TIME AS OF selector (if any)
     * @param scanParams    the reference's {@code @branch}/{@code @tag} selector (if any)
     * @return MvccSnapshot
     */
    public static Optional<MvccSnapshot> getSnapshotFromContext(TableIf tableIf,
            Optional<TableSnapshot> tableSnapshot, Optional<TableScanParams> scanParams) {
        ConnectContext connectContext = ConnectContext.get();
        if (connectContext == null) {
            return Optional.empty();
        }
        StatementContext statementContext = connectContext.getStatementContext();
        if (statementContext == null) {
            return Optional.empty();
        }
        return statementContext.getSnapshot(tableIf, tableSnapshot, scanParams);
    }
}