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Allow SQL Server JSON mapping to non-max nvarchar #37425

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roji merged 2 commits into from
Jan 3, 2026
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Allow SQL Server JSON mapping to non-max nvarchar #37425

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Allow SQL Server JSON mapping to non-max nvarchar
roji Dec 29, 2025
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roji Dec 31, 2025
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4 changes: 2 additions & 2 deletions src/EFCore.SqlServer/Storage/Internal/SqlServerTypeMappingSource.cs
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Expand Up @@ -237,10 +237,10 @@ static SqlServerTypeMappingSource()
if (clrType == typeof(JsonTypePlaceholder))
{
// We get here when a structural type (complex type or owned entity) is mapped to JSON.
return storeTypeName switch
return mappingInfo.StoreTypeNameBase switch
{
"json" => SqlServerStructuralJsonTypeMapping.JsonTypeDefault,
"nvarchar(max)" => SqlServerStructuralJsonTypeMapping.NvarcharMaxDefault,
"nvarchar" => SqlServerStructuralJsonTypeMapping.NvarcharMaxDefault,
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@AndriySvyryd AndriySvyryd Dec 30, 2025

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If it's not nvarchar(max) you'd need to create a new mapping with the specified length as it's done for strings below

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@roji roji Dec 30, 2025

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Good catch, thanks.

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@roji roji Dec 31, 2025

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@AndriySvyryd on a deeper look...

First, the current behavior seems to be the same thing we had in 9.0, i.e. return an nvarchar(max) mapping that then gets cloned with the correct length facet (so the returned store type is indeed nvarchar(2000), not max).

Second, IIUC, if the user explicitly specifies a store type, for strings as well we don't go through the creation of a new string type mapping via the code you're referring to; we find nvarchar(max) or nvarchar (the base store type) in _storeTypeMappings, and then just return that (that gets cloned with the right size outside of SqlServerTypeMappingSource).

The "complicated" fragment which constructs new SqlStringStringTypeMappings kicks in only when there's no store type configured, and allows users to optionally specify the size via data annotations/fluent API. But I don't think we allow MaxLength to be configured on complex properties (they're not regular properties). In other words, if users want a non-max nvarchar, they have to currently specify the store type fully and directly, rather than rely on size data annotation/fluent API.

So I think the current thing is in line with what we're already doing for strings, but this is a tricky area, so definitely take a look and let me know what you think.

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@AndriySvyryd AndriySvyryd Jan 2, 2026

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The "complicated" fragment which constructs new SqlStringStringTypeMappings kicks in only when there's no store type configured, and allows users to optionally specify the size via data annotations/fluent API. But I don't think we allow MaxLength to be configured on complex properties (they're not regular properties).

Sure, but we'll have to do it when #28591 is implemented. My preference is to have future-proof logic, but if you are going to port this this 10, then the simpler fix is better

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@roji roji Jan 3, 2026 •
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Let's go with the simple fix for now - I'm thinking we should maybe patch this, as it's affecting multiple users, and there isn't a really good workaround (aside from manually editing all migrations to remove the size). What's your opinion?

BTW #28591 seems to be far less relevant, now that SQL Server has a dedicated json type (and so do most/all other databases which support JSON). We should generally start viewing nvarchar JSON mapping as legacy, in the same way that SQL Server does. And although in theory json columns can have facets, in practice they don't... So I wouldn't worry too much about this.


null when _isJsonTypeSupported => SqlServerStructuralJsonTypeMapping.JsonTypeDefault,
null => SqlServerStructuralJsonTypeMapping.NvarcharMaxDefault,
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14 changes: 14 additions & 0 deletions test/EFCore.SqlServer.Tests/Storage/SqlServerTypeMappingSourceTest.cs
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Expand Up @@ -1602,6 +1602,20 @@ public void Json_is_mapped_to_nvarchar_with_compatibility_level_170_when_explici
Assert.Equal("nvarchar(max)", typeMappingSource.FindMapping(typeof(int[]), "nvarchar(max)").StoreType);
}

[ConditionalFact]
public void Json_can_be_mapped_to_nvarchar_non_max()
{
var typeMappingSource = CreateTypeMappingSource(o => o.UseSqlServer());

Assert.Equal(
"nvarchar(2000)",
typeMappingSource.FindMapping(typeof(JsonTypePlaceholder), storeTypeName: "nvarchar(2000)").StoreType);

Assert.Equal(
"nvarchar(2000)",
typeMappingSource.FindMapping(typeof(int[]), storeTypeName: "nvarchar(2000)").StoreType);
}

private SqlServerTypeMappingSource CreateTypeMappingSource(Action<DbContextOptionsBuilder> optionsAction = null)
{
var optionsBuilder = new DbContextOptionsBuilder();
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