Dictionary query support

    Fixes #212

src/EFCore.PG/Extensions/DbFunctionsExtensions/NpgsqlDictionaryDbFunctionsExtensions.cs

@@ -0,0 +1,126 @@
+// ReSharper disable once CheckNamespace
+
+namespace Microsoft.EntityFrameworkCore;
+
+/// <summary>
+/// Provides extension methods supporting `Dictionary&lt;TKey,TValue>` and `ImmutableDictionary&lt;TKey,TValue>` function translation for PostgreSQL for the `hstore`, `json` and `jsonb` store types.
+/// </summary>
+public static class NpgsqlDictionaryDbFunctionsExtensions
+{
+    /// <summary>
+    /// Deletes keys from input operand Dictionary. Returns the same store type as the provided input for `hstore` and `jsonb` columns.
+    ///
+    /// Works with `hstore`, `json` and `jsonb` type columns
+    /// <br/>
+    /// SQL translation: input - key
+    ///
+    /// Note: for `json` type columns, input will be cast to `jsonb` and will output `jsonb` which requires PostgreSQL 9.3
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input dictionary.</param>
+    /// <param name="key">The key to remove.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static T Remove<T, TValue>(this DbFunctions _, T input, string key)
+        where T : IEnumerable<KeyValuePair<string, TValue>>
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(Remove)));
+
+    /// <summary>
+    /// Converts string dictionary to an array of alternating keys and values.
+    /// <br/>
+    /// HStore SQL translation: hstore_to_array(input)
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input hstore.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static List<string> ToKeyValueList(this DbFunctions _, IEnumerable<KeyValuePair<string, string>> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(ToKeyValueList)));
+
+    /// <summary>
+    /// Constructs an hstore `Dictionary&lt;string, string>` from a key/value pair string array
+    /// <br/>
+    /// SQL translation: hstore(input)
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input string array of key value pairs.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, string> DictionaryFromKeyValueList(this DbFunctions _, IList<string> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(DictionaryFromKeyValueList)));
+
+    /// <summary>
+    /// Constructs an hstore `Dictionary&lt;string, string>` from a string array of keys and a string array of values
+    /// <br/>
+    /// SQL translation: hstore(keys, values)
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="keys">The input string array of keys.</param>
+    /// <param name="values">The input string array of values.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, string> DictionaryFromKeysAndValues(this DbFunctions _, IList<string> keys, IList<string> values)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(DictionaryFromKeysAndValues)));
+
+    /// <summary>
+    /// Converts an `hstore` to a `json` value type `Dictionary&lt;string, object?>`, but attempts to distinguish numerical and boolean values so they are unquoted in the JSON.
+    /// <br/>
+    /// SQL translation: hstore_to_json_loose(input)
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input hstore.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, object?> ToJsonLoose(this DbFunctions _, IEnumerable<KeyValuePair<string, string>> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(ToJsonLoose)));
+
+    /// <summary>
+    /// Converts an `hstore` to a `jsonb` value type `Dictionary&lt;string, object?>`, but attempts to distinguish numerical and boolean values so they are unquoted in the JSON.
+    /// <br/>
+    /// SQL translation: hstore_to_jsonb_loose(input)
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input hstore.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, object?> ToJsonbLoose(this DbFunctions _, IEnumerable<KeyValuePair<string, string>> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(ToJsonbLoose)));
+
+    /// <summary>
+    /// Converts a `json` or `jsonb` type `IEnumerable&lt;KeyValuePair&lt;string, string>>` (i.e. Dictionary&lt;string, string>> or related type) to an hstore type `Dictionary&lt;string, string>>`
+    /// <br/>
+    /// Can be used during a migration of changing a column's StoreType from 'json' to 'hstore' with the `Using` clause
+    ///
+    /// HStore SQL translation: input
+    /// Json SQL translation: select hstore(array_agg(key), array_agg(value)) FROM json_each_text(input)
+    /// Json SQL translation: select hstore(array_agg(key), array_agg(value)) FROM jsonb_each_text(input)
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input hstore.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, string> ToHstore(this DbFunctions _, IEnumerable<KeyValuePair<string, string>> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(ToHstore)));
+
+    /// <summary>
+    /// Converts an `jsonb` or `hstore` type value to a `jsonb` type `Dictionary&lt;TKey, TKey>`
+    /// <br/>
+    ///
+    /// Hstore SQL translation: hstore_to_json(input)
+    /// Json SQL translation: input
+    /// Jsonb SQL translation: input::json
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input hstore.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, TValue> ToJson<TValue>(this DbFunctions _, IEnumerable<KeyValuePair<string, TValue>> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(ToJson)));
+
+    /// <summary>
+    /// Converts an `hstore` or `json` type value to a `jsonb` type `Dictionary&lt;TKey, TValue>`
+    ///
+    /// Can be used during a migration of changing a column's StoreType from 'hstore' to 'jsonb' with the `Using` clause
+    /// <br/>
+    /// HStore SQL translation: hstore_to_jsonb(input)
+    /// Json SQL translation: input::jsonb
+    /// Jsonb SQL translation: input
+    /// </summary>
+    /// <param name="_">The <see cref="DbFunctions" /> instance.</param>
+    /// <param name="input">The input hstore.</param>
+    /// <seealso href="https://www.postgresql.org/docs/current/hstore.html#HSTORE-OPS-FUNCS">PostgreSQL documentation for 'hstore' functions.</seealso>
+    public static Dictionary<string, TValue> ToJsonb<TValue>(this DbFunctions _, IEnumerable<KeyValuePair<string, TValue>> input)
+        => throw new InvalidOperationException(CoreStrings.FunctionOnClient(nameof(ToJsonb)));
+}