FREEZE tbl1[, tbl2, ...]FREEZE readies a real-time/plain table for a secure backup. Specifically, it: 1. Deactivates table compaction. If the table is currently being compacted, FREEZE will wait for completion. 2. Transfers the current RAM chunk to a disk chunk. 3. Flushes attributes. 4. Disables implicit operations that could modify the disk files. 5. Shows the actual file list associated with the table.
The built-in tool manticore-backup uses FREEZE to ensure data consistency. You can do the same if you want to create your own backup solution or need to freeze tables for other reasons. Just follow these steps: 1. FREEZE a table (or a few). 2. Capture the output of the FREEZE command and back up the specified files. 3. UNFREEZE the table(s) once finished.
FREEZE t;+-------------------+---------------------------------+
| file | normalized |
+-------------------+---------------------------------+
| data/t/t.0.spa | /work/anytest/data/t/t.0.spa |
| data/t/t.0.spd | /work/anytest/data/t/t.0.spd |
| data/t/t.0.spds | /work/anytest/data/t/t.0.spds |
| data/t/t.0.spe | /work/anytest/data/t/t.0.spe |
| data/t/t.0.sph | /work/anytest/data/t/t.0.sph |
| data/t/t.0.sphi | /work/anytest/data/t/t.0.sphi |
| data/t/t.0.spi | /work/anytest/data/t/t.0.spi |
| data/t/t.0.spm | /work/anytest/data/t/t.0.spm |
| data/t/t.0.spp | /work/anytest/data/t/t.0.spp |
| data/t/t.0.spt | /work/anytest/data/t/t.0.spt |
| data/t/t.meta | /work/anytest/data/t/t.meta |
| data/t/t.ram | /work/anytest/data/t/t.ram |
| data/t/t.settings | /work/anytest/data/t/t.settings |
+-------------------+---------------------------------+
13 rows in set (0.01 sec)The file column indicates the table’s file paths within the data_dir of the running instance. The normalized column displays the absolute paths for the same files. To back up a table, simply copy the provided files without additional preparation.
When a table is frozen, you cannot execute UPDATE queries; they will fail with the error message “index is locked now, try again later.”
Also, DELETE and REPLACE queries have some restrictions while the table is frozen: * If DELETE affects a document in the current RAM chunk - it is permitted. * If DELETE impacts a document in a disk chunk but was previously deleted - it is allowed. * If DELETE would alter an actual disk chunk - it will wait until the table is unfrozen.
Manually FLUSHing a RAM chunk of a frozen table will report ‘success’, but no real saving will occur.
DROP/TRUNCATE of a frozen table is allowed since these operations are not implicit. We assume that if you truncate or drop a table, you don’t need it backed up; therefore, it should not have been frozen initially.
INSERTing into a frozen table is supported but limited: new data will be stored in RAM (as usual) until rt_mem_limit is reached; then, new insertions will wait until the table is unfrozen.
If you shut down the daemon with a frozen table, it will act as if it experienced a dirty shutdown (e.g., kill -9): newly inserted data will not be saved in the RAM-chunk on disk, and upon restart, it will be restored from a binary log (if any) or lost (if binary logging is disabled).
UNFREEZE tbl1[, tbl2, ...]UNFREEZE reactivates previously blocked operations and resumes the internal compaction service. All operations waiting for a table to unfreeze will also be unfrozen and complete normally.
UNFREEZE tbl;