Tweaks

proxy/src/http/pg_to_json.rs

@@ -0,0 +1,138 @@
+
+use anyhow::{anyhow, Context};
+use serde_json::Map;
+use tokio_postgres::{
+    types::{FromSql, Type},
+    Column, Row,
+};
+
+// some type-aliases I use in my project
+pub type JSONValue = serde_json::Value;
+pub type RowData = Map<String, JSONValue>;
+pub type Error = anyhow::Error; // from: https://github.com/dtolnay/anyhow
+
+pub fn postgres_row_to_json_value(row: Row) -> Result<JSONValue, Error> {
+    let row_data = postgres_row_to_row_data(row)?;
+    Ok(JSONValue::Object(row_data))
+}
+
+pub fn postgres_row_to_row_data(row: Row) -> Result<RowData, Error> {
+    let mut result: Map<String, JSONValue> = Map::new();
+    for (i, column) in row.columns().iter().enumerate() {
+        let name = column.name();
+        let json_value = pg_cell_to_json_value(&row, column, i)?;
+        result.insert(name.to_string(), json_value);
+    }
+    Ok(result)
+}
+
+pub fn pg_cell_to_json_value(
+    row: &Row,
+    column: &Column,
+    column_i: usize,
+) -> Result<JSONValue, Error> {
+    let f64_to_json_number = |raw_val: f64| -> Result<JSONValue, Error> {
+        let temp = serde_json::Number::from_f64(raw_val).ok_or(anyhow!("invalid json-float"))?;
+        Ok(JSONValue::Number(temp))
+    };
+    Ok(match *column.type_() {
+        // for rust-postgres <> postgres type-mappings: https://docs.rs/postgres/latest/postgres/types/trait.FromSql.html#types
+        // for postgres types: https://www.postgresql.org/docs/7.4/datatype.html#DATATYPE-TABLE
+
+        // single types
+        Type::BOOL => get_basic(row, column, column_i, |a: bool| Ok(JSONValue::Bool(a)))?,
+        Type::INT2 => get_basic(row, column, column_i, |a: i16| {
+            Ok(JSONValue::Number(serde_json::Number::from(a)))
+        })?,
+        Type::INT4 => get_basic(row, column, column_i, |a: i32| {
+            Ok(JSONValue::Number(serde_json::Number::from(a)))
+        })?,
+        Type::INT8 => get_basic(row, column, column_i, |a: i64| {
+            Ok(JSONValue::Number(serde_json::Number::from(a)))
+        })?,
+        Type::TEXT | Type::VARCHAR => {
+            get_basic(row, column, column_i, |a: String| Ok(JSONValue::String(a)))?
+        }
+        // Type::JSON | Type::JSONB => get_basic(row, column, column_i, |a: JSONValue| Ok(a))?,
+        Type::FLOAT4 => get_basic(row, column, column_i, |a: f32| f64_to_json_number(a.into()))?,
+        Type::FLOAT8 => get_basic(row, column, column_i, f64_to_json_number)?,
+        // these types require a custom StringCollector struct as an intermediary (see struct at bottom)
+        Type::TS_VECTOR => get_basic(row, column, column_i, |a: StringCollector| {
+            Ok(JSONValue::String(a.0))
+        })?,
+
+        // array types
+        Type::BOOL_ARRAY => get_array(row, column, column_i, |a: bool| Ok(JSONValue::Bool(a)))?,
+        Type::INT2_ARRAY => get_array(row, column, column_i, |a: i16| {
+            Ok(JSONValue::Number(serde_json::Number::from(a)))
+        })?,
+        Type::INT4_ARRAY => get_array(row, column, column_i, |a: i32| {
+            Ok(JSONValue::Number(serde_json::Number::from(a)))
+        })?,
+        Type::INT8_ARRAY => get_array(row, column, column_i, |a: i64| {
+            Ok(JSONValue::Number(serde_json::Number::from(a)))
+        })?,
+        Type::TEXT_ARRAY | Type::VARCHAR_ARRAY => {
+            get_array(row, column, column_i, |a: String| Ok(JSONValue::String(a)))?
+        }
+        // Type::JSON_ARRAY | Type::JSONB_ARRAY => get_array(row, column, column_i, |a: JSONValue| Ok(a))?,
+        Type::FLOAT4_ARRAY => get_array(row, column, column_i, f64_to_json_number)?,
+        Type::FLOAT8_ARRAY => get_array(row, column, column_i, f64_to_json_number)?,
+        // these types require a custom StringCollector struct as an intermediary (see struct at bottom)
+        Type::TS_VECTOR_ARRAY => get_array(row, column, column_i, |a: StringCollector| {
+            Ok(JSONValue::String(a.0))
+        })?,
+
+        _ => anyhow::bail!(
+            "Cannot convert pg-cell \"{}\" of type \"{}\" to a JSONValue.",
+            column.name(),
+            column.type_().name()
+        ),
+    })
+}
+
+fn get_basic<'a, T: FromSql<'a>>(
+    row: &'a Row,
+    column: &Column,
+    column_i: usize,
+    val_to_json_val: impl Fn(T) -> Result<JSONValue, Error>,
+) -> Result<JSONValue, Error> {
+    let raw_val = row
+        .try_get::<_, Option<T>>(column_i)
+        .with_context(|| format!("column_name:{}", column.name()))?;
+    raw_val.map_or(Ok(JSONValue::Null), val_to_json_val)
+}
+fn get_array<'a, T: FromSql<'a>>(
+    row: &'a Row,
+    column: &Column,
+    column_i: usize,
+    val_to_json_val: impl Fn(T) -> Result<JSONValue, Error>,
+) -> Result<JSONValue, Error> {
+    let raw_val_array = row
+        .try_get::<_, Option<Vec<T>>>(column_i)
+        .with_context(|| format!("column_name:{}", column.name()))?;
+    Ok(match raw_val_array {
+        Some(val_array) => {
+            let mut result = vec![];
+            for val in val_array {
+                result.push(val_to_json_val(val)?);
+            }
+            JSONValue::Array(result)
+        }
+        None => JSONValue::Null,
+    })
+}
+
+struct StringCollector(String);
+impl FromSql<'_> for StringCollector {
+    fn from_sql(
+        _: &Type,
+        raw: &[u8],
+    ) -> Result<StringCollector, Box<dyn std::error::Error + Sync + Send>> {
+        let result = std::str::from_utf8(raw)?;
+        Ok(StringCollector(result.to_owned()))
+    }
+    fn accepts(_ty: &Type) -> bool {
+        true
+    }
+}