Raise an error when too-large chunks are encountered

Closes #217

Author: jeromekelleher

bio2zarr/vcf2zarr/vcz.py

@@ -34,7 +34,7 @@ def inspect(path):
 
 
 @dataclasses.dataclass
-class ZarrColumnSpec:
+class ZarrArraySpec:
     name: str
     dtype: str
     shape: tuple
@@ -54,7 +54,7 @@ def __post_init__(self):
 
     @staticmethod
     def new(**kwargs):
-        spec = ZarrColumnSpec(
+        spec = ZarrArraySpec(
             **kwargs, compressor=DEFAULT_ZARR_COMPRESSOR.get_config(), filters=[]
         )
         spec._choose_compressor_settings()
@@ -94,7 +94,7 @@ def from_field(
                 dimensions.append("genotypes")
             else:
                 dimensions.append(f"{vcf_field.category}_{vcf_field.name}_dim")
-        return ZarrColumnSpec.new(
+        return ZarrArraySpec.new(
             vcf_field=vcf_field.full_name,
             name=variable_name,
             dtype=vcf_field.smallest_dtype(),
@@ -127,6 +127,23 @@ def _choose_compressor_settings(self):
 
         self.compressor["shuffle"] = shuffle
 
+    @property
+    def chunk_nbytes(self):
+        """
+        Returns the nbytes for a single chunk in this array.
+        """
+        items = 1
+        dim = 0
+        for chunk_size in self.chunks:
+            size = min(chunk_size, self.shape[dim])
+            items *= size
+            dim += 1
+        # Include sizes for extra dimensions.
+        for size in self.shape[dim:]:
+            items *= size
+        dt = np.dtype(self.dtype)
+        return items * dt.itemsize
+
     @property
     def variant_chunk_nbytes(self):
         """
@@ -157,6 +174,24 @@ class VcfZarrSchema(core.JsonDataclass):
     filters: list
     fields: list
 
+    def validate(self):
+        """
+        Checks that the schema is well-formed and within required limits.
+        """
+        for field in self.fields:
+            # This is the Blosc max buffer size
+            if field.chunk_nbytes > 2147483647:
+                # TODO add some links to documentation here advising how to
+                # deal with PL values.
+                raise ValueError(
+                    f"Field {field.name} chunks are too large "
+                    f"({field.chunk_nbytes} > 2**31 - 1 bytes). "
+                    "Either generate a schema and drop this field (if you don't "
+                    "need it) or reduce the variant or sample chunk sizes."
+                )
+            # TODO other checks? There must be lots of ways people could mess
+            # up the schema leading to cryptic errors.
+
     def field_map(self):
         return {field.name: field for field in self.fields}
 
@@ -171,7 +206,7 @@ def fromdict(d):
         ret.samples = [icf.Sample(**sd) for sd in d["samples"]]
         ret.contigs = [icf.Contig(**sd) for sd in d["contigs"]]
         ret.filters = [icf.Filter(**sd) for sd in d["filters"]]
-        ret.fields = [ZarrColumnSpec(**sd) for sd in d["fields"]]
+        ret.fields = [ZarrArraySpec(**sd) for sd in d["fields"]]
         return ret
 
     @staticmethod
@@ -192,7 +227,7 @@ def generate(icf, variants_chunk_size=None, samples_chunk_size=None):
         )
 
         def spec_from_field(field, variable_name=None):
-            return ZarrColumnSpec.from_field(
+            return ZarrArraySpec.from_field(
                 field,
                 num_samples=n,
                 num_variants=m,
@@ -204,7 +239,7 @@ def spec_from_field(field, variable_name=None):
         def fixed_field_spec(
             name, dtype, vcf_field=None, shape=(m,), dimensions=("variants",)
         ):
-            return ZarrColumnSpec.new(
+            return ZarrArraySpec.new(
                 vcf_field=vcf_field,
                 name=name,
                 dtype=dtype,
@@ -230,13 +265,13 @@ def fixed_field_spec(
             ),
             fixed_field_spec(
                 name="variant_allele",
-                dtype="str",
+                dtype="O",
                 shape=(m, max_alleles),
                 dimensions=["variants", "alleles"],
             ),
             fixed_field_spec(
                 name="variant_id",
-                dtype="str",
+                dtype="O",
             ),
             fixed_field_spec(
                 name="variant_id_mask",
@@ -267,7 +302,7 @@ def fixed_field_spec(
             chunks = [variants_chunk_size, samples_chunk_size]
             dimensions = ["variants", "samples"]
             colspecs.append(
-                ZarrColumnSpec.new(
+                ZarrArraySpec.new(
                     vcf_field=None,
                     name="call_genotype_phased",
                     dtype="bool",
@@ -280,7 +315,7 @@ def fixed_field_spec(
             shape += [ploidy]
             dimensions += ["ploidy"]
             colspecs.append(
-                ZarrColumnSpec.new(
+                ZarrArraySpec.new(
                     vcf_field=None,
                     name="call_genotype",
                     dtype=gt_field.smallest_dtype(),
@@ -291,7 +326,7 @@ def fixed_field_spec(
                 )
             )
             colspecs.append(
-                ZarrColumnSpec.new(
+                ZarrArraySpec.new(
                     vcf_field=None,
                     name="call_genotype_mask",
                     dtype="bool",
@@ -447,6 +482,7 @@ def init(
         self.icf = icf
         if self.path.exists():
             raise ValueError("Zarr path already exists")  # NEEDS TEST
+        schema.validate()
         partitions = VcfZarrPartition.generate_partitions(
             self.icf.num_records,
             schema.variants_chunk_size,

tests/test_vcz.py

@@ -67,7 +67,7 @@ def test_not_enough_memory(self, tmp_path, icf_path, max_memory):
         with pytest.raises(ValueError, match="Insufficient memory"):
             vcf2zarr.encode(icf_path, zarr_path, max_memory=max_memory)
 
-    @pytest.mark.parametrize("max_memory", ["150KiB", "200KiB"])
+    @pytest.mark.parametrize("max_memory", ["315KiB", "500KiB"])
     def test_not_enough_memory_for_two(
         self, tmp_path, icf_path, zarr_path, caplog, max_memory
     ):
@@ -214,6 +214,55 @@ def get_field_dict(a_schema, name):
             return field
 
 
+class TestChunkNbytes:
+    @pytest.mark.parametrize(
+        ("field", "value"),
+        [
+            ("call_genotype", 54),  # 9 * 3 * 2 * 1
+            ("call_genotype_phased", 27),
+            ("call_genotype_mask", 54),
+            ("variant_position", 36),  # 9 * 4
+            ("variant_H2", 9),
+            ("variant_AC", 18),  # 9 * 2
+            # Object fields have an itemsize of 8
+            ("variant_AA", 72),  # 9 * 8
+            ("variant_allele", 9 * 4 * 8),
+        ],
+    )
+    def test_example_schema(self, schema, field, value):
+        field = schema.field_map()[field]
+        assert field.chunk_nbytes == value
+
+    def test_chunk_size(self, icf_path, tmp_path):
+        store = vcf2zarr.IntermediateColumnarFormat(icf_path)
+        schema = vcf2zarr.VcfZarrSchema.generate(
+            store, samples_chunk_size=2, variants_chunk_size=3
+        )
+        fields = schema.field_map()
+        assert fields["call_genotype"].chunk_nbytes == 3 * 2 * 2
+        assert fields["variant_position"].chunk_nbytes == 3 * 4
+        assert fields["variant_AC"].chunk_nbytes == 3 * 2
+
+
+class TestValidateSchema:
+    @pytest.mark.parametrize("size", [2**31, 2**31 + 1, 2**32])
+    def test_chunk_too_large(self, schema, size):
+        schema = vcf2zarr.VcfZarrSchema.fromdict(schema.asdict())
+        field = schema.field_map()["variant_H2"]
+        field.shape = (size,)
+        field.chunks = (size,)
+        with pytest.raises(ValueError, match="Field variant_H2 chunks are too large"):
+            schema.validate()
+
+    @pytest.mark.parametrize("size", [2**31 - 1, 2**30])
+    def test_chunk_not_too_large(self, schema, size):
+        schema = vcf2zarr.VcfZarrSchema.fromdict(schema.asdict())
+        field = schema.field_map()["variant_H2"]
+        field.shape = (size,)
+        field.chunks = (size,)
+        schema.validate()
+
+
 class TestDefaultSchema:
     def test_format_version(self, schema):
         assert schema.format_version == vcz_mod.ZARR_SCHEMA_FORMAT_VERSION
@@ -359,16 +408,17 @@ class TestVcfDescriptions:
     def test_fields(self, schema, field, description):
         assert schema.field_map()[field].description == description
 
-    # This information is not in the schema yet,
-    # https://github.com/sgkit-dev/vcf2zarr/issues/123
-    # @pytest.mark.parametrize(
-    #     ("filt", "description"),
-    #     [
-    #         ("s50","Less than 50% of samples have data"),
-    #         ("q10", "Quality below 10"),
-    #     ])
-    # def test_filters(self, schema, filt, description):
-    #     assert schema["filters"][field]["description"] == description
+    @pytest.mark.parametrize(
+        ("filt", "description"),
+        [
+            ("PASS", "All filters passed"),
+            ("s50", "Less than 50% of samples have data"),
+            ("q10", "Quality below 10"),
+        ],
+    )
+    def test_filters(self, schema, filt, description):
+        d = {f.id: f.description for f in schema.filters}
+        assert d[filt] == description
 
 
 class TestVcfZarrWriterExample: