OMERO.tables

OMERO.tables stores columnar analysis data as an OriginalFile backed by an HDF table. Treat table reads as data exports and table creation/update as server writes.

Compatibility and Scope

The current stable OMERO.tables definition is part of omero-blitz 5.8.5 in the OMERO.server 5.6.18 documentation. OMERO.server 5.6.12 specifically required OMERO.py 5.19.4 for the Tables service to start correctly, which illustrates why client/server pairing matters.

Before using tables:

confirm the server's tested OMERO.py version;
confirm the Tables service is active;
select one group and one table/attached object;
cap columns and rows;
plan handle closure even after read/query failure.

Column Types

Current scalar columns:

FileColumn, ImageColumn, RoiColumn, WellColumn, PlateColumn
BoolColumn
LongColumn (signed 64-bit)
DoubleColumn (64-bit)
StringColumn(name, description, size, values)

Current fixed-width array columns include:

FloatArrayColumn(name, description, size, values)
DoubleArrayColumn(name, description, size, values)
LongArrayColumn(name, description, size, values)

The array size argument is required. Older examples that omit it are stale. All columns added in one operation must contain the same number of rows. Column names are unique; names beginning with double underscore are reserved.

The service performs limited validation of string and array lengths. Validate every value against the initialized schema before writing.

Read-Only Table Inspection

Start from one explicit OriginalFile ID, not a filename search:

original_file_id = 123
max_rows = 100
max_columns = 20

original = conn.getObject("OriginalFile", original_file_id)
if original is None:
    raise LookupError("Table OriginalFile unavailable")

resources = conn.c.sf.sharedResources()
table = resources.openTable(original._obj)
try:
    headers = list(table.getHeaders())
    if len(headers) > max_columns:
        raise ValueError("Table has more columns than approved")

    row_count = table.getNumberOfRows()
    stop = min(row_count, max_rows)
    column_indices = list(range(len(headers)))
    data = table.read(column_indices, 0, stop)

    print(
        {
            "original_file_id": original_file_id,
            "total_rows": row_count,
            "returned_rows": stop,
            "truncated": row_count > stop,
            "columns": [column.name for column in headers],
        }
    )
finally:
    table.close()

read(colNumbers, start, stop) uses a stop-exclusive row range, except the current docs note that start=0, stop=0 returns the first row. Avoid that edge case: do not call read when the approved row count is zero.

Paged Read

Read consecutive chunks instead of every row:

def iter_table_pages(table, column_indices, *, limit=1000, page_size=100):
    if not 1 <= limit <= 10_000:
        raise ValueError("limit out of range")
    if not 1 <= page_size <= min(limit, 500):
        raise ValueError("page_size out of range")

    total = min(table.getNumberOfRows(), limit)
    start = 0
    while start < total:
        stop = min(start + page_size, total)
        yield table.read(column_indices, start, stop)
        start = stop

Do not accumulate all pages unless the total cap and memory cost were reviewed. Large string/array columns can make a small row count expensive.

Fixed Queries and Bound Variables

OMERO.tables uses PyTables condition syntax. Keep the condition code fixed and bind user values:

from omero.rtypes import rint

row_count = table.getNumberOfRows()
max_rows_considered = min(row_count, 1000)
matches = table.getWhereList(
    condition="(Image > minimum_id)",
    variables={"minimum_id": rint(100)},
    start=0,
    stop=max_rows_considered,
    step=0,
)
matches = list(matches[:100])
data = table.readCoordinates(matches)

Never concatenate user text into a condition. Validate column names against getHeaders() and map requested operations to a fixed allowlist.

The documented condition language includes logical, comparison, arithmetic, and selected mathematical operations. Treat it as a query language, not as arbitrary Python. Do not use Python eval() or exec() around it.

Creating a Table

Creation is a write. Use a unique, caller-reviewed name and one selected repository:

from omero.grid import DoubleColumn, ImageColumn, StringColumn

columns = [
    ImageColumn("Image", "Source image", []),
    DoubleColumn("MeanIntensity", "Mean raw value", []),
    StringColumn("Status", "Review status", 32, []),
]

resources = conn.c.sf.sharedResources()
repositories = resources.repositories().descriptions
if not repositories:
    raise RuntimeError("No table repository is available")

repository_id = repositories[0].getId().getValue()
table = resources.newTable(repository_id, "analysis-v2-explicit-name")
try:
    table.initialize(columns)
    table.addData(
        [
            ImageColumn("Image", "Source image", [101, 102]),
            DoubleColumn("MeanIntensity", "Mean raw value", [12.5, 14.0]),
            StringColumn("Status", "Review status", 32, ["reviewed", "reviewed"]),
        ]
    )
    table_file_id = table.getOriginalFile().getId().getValue()
finally:
    table.close()

Before execution:

verify repository selection with the administrator;
validate every referenced object ID in the same intended group;
validate all row counts, numeric ranges, strings, and array sizes;
cap rows per addData batch;
decide recovery if initialization succeeds but data upload fails.

Linking a Table

The table OriginalFile becomes discoverable through a FileAnnotation and an object-annotation link:

from omero.model import (
    DatasetAnnotationLinkI,
    DatasetI,
    FileAnnotationI,
    OriginalFileI,
)

file_annotation = FileAnnotationI()
file_annotation.setFile(OriginalFileI(table_file_id, False))
file_annotation = conn.getUpdateService().saveAndReturnObject(file_annotation)

link = DatasetAnnotationLinkI()
link.setParent(DatasetI(dataset_id, False))
link.setChild(FileAnnotationI(file_annotation.getId().getValue(), False))
conn.getUpdateService().saveAndReturnObject(link)

This is a second write after table creation. If link creation fails, the table and file annotation may remain orphaned. Record IDs after every successful step and define cleanup before starting.

OMERO.web table viewing expects conventions such as a column named Image with a supported ID/numeric column type. A custom column called something else may store valid data but not receive the same UI behavior.

Concurrency and Lifecycle

Each OMERO table is backed by one HDF table. PyTables/HDF does not support general concurrent access, so OMERO.tables adds global locking. Keep table handles short-lived:

table = resources.openTable(original._obj)
try:
    # One bounded operation.
    ...
finally:
    table.close()

Do not hold a handle across:

user interaction;
network retries/reconnection;
long pixel analysis;
another process's expected write window.

If BlitzGateway reconnects, discard any old table proxy and open a fresh one.

Updating or Deleting

addData() and update() mutate table content. Deleting the backing OriginalFile may remove the table; deleting one annotation link may merely detach it from one object. These require separate impact review.

Never:

update rows selected by a dynamically constructed condition;
append an unbounded result set;
delete a table based only on filename;
overwrite an existing table as a retry strategy;
leave a handle open after an exception.

Table Checklist

Explicit OriginalFile ID and selected group
Server/client pairing verified
Column count, row limit, page size, string size, and array width bounded
Fixed conditions with bound variables
No empty selection that means “all”
Handle closed in finally
Writes and links reviewed separately
Partial-create IDs recorded for recovery
Export classification reviewed before JSON/CSV output