Adds Parquet Metadata Inspection Udfs

- adds "parquet.schema" udf to inspect the schema of a parquet file,
- adds "parquet.metadata", "parquet.file_metadata", and "parquet.kv_metadata" udfs to inspect the metadata of a parquet file.

src/lib.rs

@@ -4,6 +4,7 @@ use pgrx::{prelude::*, GucContext, GucFlags, GucRegistry};
 
 mod arrow_parquet;
 mod parquet_copy_hook;
+mod parquet_udfs;
 mod pgrx_utils;
 mod type_compat;
 

src/parquet_udfs.rs

@@ -0,0 +1,2 @@
+pub(crate) mod metadata;
+pub(crate) mod schema;

src/parquet_udfs/metadata.rs

@@ -0,0 +1,268 @@
+use ::parquet::file::statistics::Statistics;
+use pgrx::{iter::TableIterator, name, pg_extern, pg_schema};
+
+use crate::arrow_parquet::uri_utils::{parquet_metadata_from_uri, parse_uri, uri_as_string};
+
+#[pg_schema]
+mod parquet {
+    use super::*;
+
+    #[pg_extern]
+    #[allow(clippy::type_complexity)]
+    fn metadata(
+        uri: String,
+    ) -> TableIterator<
+        'static,
+        (
+            name!(uri, String),
+            name!(row_group_id, i64),
+            name!(row_group_num_rows, i64),
+            name!(row_group_num_columns, i64),
+            name!(row_group_bytes, i64),
+            name!(column_id, i64),
+            name!(file_offset, i64),
+            name!(num_values, i64),
+            name!(path_in_schema, String),
+            name!(type_name, String),
+            name!(stats_null_count, Option<i64>),
+            name!(stats_distinct_count, Option<i64>),
+            name!(stats_min, Option<String>),
+            name!(stats_max, Option<String>),
+            name!(compression, String),
+            name!(encodings, String),
+            name!(index_page_offset, Option<i64>),
+            name!(dictionary_page_offset, Option<i64>),
+            name!(data_page_offset, i64),
+            name!(total_compressed_size, i64),
+            name!(total_uncompressed_size, i64),
+        ),
+    > {
+        let uri = parse_uri(&uri);
+
+        // new_current_thread runtime uses the current thread to run the tokio reactor.
+        // This uses the same thread that is running the Postgres backend.
+        let runtime = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .unwrap_or_else(|e| {
+                panic!("Failed to create tokio runtime: {}", e);
+            });
+
+        let parquet_metadata = runtime.block_on(parquet_metadata_from_uri(&uri));
+
+        let mut rows = vec![];
+
+        for (row_group_id, row_group) in parquet_metadata.row_groups().iter().enumerate() {
+            let row_group_num_rows = row_group.num_rows();
+            let row_group_num_columns = row_group.num_columns() as i64;
+            let row_group_bytes = row_group.total_byte_size();
+
+            for (column_id, column) in row_group.columns().iter().enumerate() {
+                let file_offset = column.file_offset();
+
+                let num_values = column.num_values();
+
+                let path_in_schema = column.column_path().string();
+
+                let type_name = column.column_type().to_string();
+
+                let mut stats_min = None;
+                let mut stats_max = None;
+                let mut stats_null_count = None;
+                let mut stats_distinct_count = None;
+
+                if let Some(statistics) = column.statistics() {
+                    stats_min = stats_min_value_to_str(statistics);
+
+                    stats_max = stats_max_value_to_str(statistics);
+
+                    stats_null_count = statistics.null_count_opt().map(|v| v as i64);
+
+                    stats_distinct_count = statistics.distinct_count_opt().map(|v| v as i64);
+                }
+
+                let compression = column.compression().to_string();
+
+                let encodings = column
+                    .encodings()
+                    .iter()
+                    .map(|e| e.to_string())
+                    .collect::<Vec<_>>()
+                    .join(",");
+
+                let index_page_offset = column.index_page_offset();
+
+                let dictionary_page_offset = column.dictionary_page_offset();
+
+                let data_page_offset = column.data_page_offset();
+
+                let total_compressed_size = column.compressed_size();
+
+                let total_uncompressed_size = column.uncompressed_size();
+
+                let row = (
+                    uri_as_string(&uri),
+                    row_group_id as i64,
+                    row_group_num_rows,
+                    row_group_num_columns,
+                    row_group_bytes,
+                    column_id as i64,
+                    file_offset,
+                    num_values,
+                    path_in_schema,
+                    type_name,
+                    stats_null_count,
+                    stats_distinct_count,
+                    stats_min,
+                    stats_max,
+                    compression,
+                    encodings,
+                    index_page_offset,
+                    dictionary_page_offset,
+                    data_page_offset,
+                    total_compressed_size,
+                    total_uncompressed_size,
+                );
+
+                rows.push(row);
+            }
+        }
+
+        TableIterator::new(rows)
+    }
+
+    #[pg_extern]
+    fn file_metadata(
+        uri: String,
+    ) -> TableIterator<
+        'static,
+        (
+            name!(uri, String),
+            name!(created_by, Option<String>),
+            name!(num_rows, i64),
+            name!(num_row_groups, i64),
+            name!(format_version, String),
+        ),
+    > {
+        let uri = parse_uri(&uri);
+
+        // new_current_thread runtime uses the current thread to run the tokio reactor.
+        // This uses the same thread that is running the Postgres backend.
+        let runtime = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .unwrap_or_else(|e| {
+                panic!("Failed to create tokio runtime: {}", e);
+            });
+
+        let parquet_metadata = runtime.block_on(parquet_metadata_from_uri(&uri));
+
+        let created_by = parquet_metadata
+            .file_metadata()
+            .created_by()
+            .map(|c| c.to_string());
+
+        let num_rows = parquet_metadata.file_metadata().num_rows();
+
+        let num_row_groups = parquet_metadata.num_row_groups() as i64;
+
+        let format_version = parquet_metadata.file_metadata().version().to_string();
+
+        let row = (
+            uri_as_string(&uri),
+            created_by,
+            num_rows,
+            num_row_groups,
+            format_version,
+        );
+
+        TableIterator::new(vec![row])
+    }
+
+    #[pg_extern]
+    fn kv_metadata(
+        uri: String,
+    ) -> TableIterator<
+        'static,
+        (
+            name!(uri, String),
+            name!(key, Vec<u8>),
+            name!(value, Option<Vec<u8>>),
+        ),
+    > {
+        let uri = parse_uri(&uri);
+
+        // new_current_thread runtime uses the current thread to run the tokio reactor.
+        // This uses the same thread that is running the Postgres backend.
+        let runtime = tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .unwrap_or_else(|e| {
+                panic!("Failed to create tokio runtime: {}", e);
+            });
+
+        let parquet_metadata = runtime.block_on(parquet_metadata_from_uri(&uri));
+        let kv_metadata = parquet_metadata.file_metadata().key_value_metadata();
+
+        if kv_metadata.is_none() {
+            return TableIterator::new(vec![]);
+        }
+
+        let kv_metadata = kv_metadata.expect("kv_metadata should be Some");
+
+        let mut rows = vec![];
+
+        for kv in kv_metadata {
+            let key = kv.key.as_bytes().to_owned();
+            let value = kv.value.as_ref().map(|v| v.as_bytes().to_owned());
+
+            let row = (uri_as_string(&uri), key, value);
+
+            rows.push(row);
+        }
+
+        TableIterator::new(rows)
+    }
+}
+
+fn stats_min_value_to_str(statistics: &Statistics) -> Option<String> {
+    match &statistics {
+        Statistics::Boolean(val_stats) => val_stats.min_opt().map(|v| v.to_string()),
+        Statistics::Int32(val_stats) => val_stats.min_opt().map(|v| v.to_string()),
+        Statistics::Int64(val_stats) => val_stats.min_opt().map(|v| v.to_string()),
+        Statistics::Int96(val_stats) => val_stats.min_opt().map(|v| v.to_string()),
+        Statistics::Float(val_stats) => val_stats.min_opt().map(|v| v.to_string()),
+        Statistics::Double(val_stats) => val_stats.min_opt().map(|v| v.to_string()),
+        Statistics::ByteArray(val_stats) => val_stats.min_opt().map(|v| match v.as_utf8() {
+            Ok(v) => v.to_string(),
+            Err(_) => v.to_string(),
+        }),
+        Statistics::FixedLenByteArray(val_stats) => {
+            val_stats.min_opt().map(|v| match v.as_utf8() {
+                Ok(v) => v.to_string(),
+                Err(_) => v.to_string(),
+            })
+        }
+    }
+}
+
+fn stats_max_value_to_str(statistics: &Statistics) -> Option<String> {
+    match statistics {
+        Statistics::Boolean(statistics) => statistics.max_opt().map(|v| v.to_string()),
+        Statistics::Int32(statistics) => statistics.max_opt().map(|v| v.to_string()),
+        Statistics::Int64(statistics) => statistics.max_opt().map(|v| v.to_string()),
+        Statistics::Int96(statistics) => statistics.max_opt().map(|v| v.to_string()),
+        Statistics::Float(statistics) => statistics.max_opt().map(|v| v.to_string()),
+        Statistics::Double(statistics) => statistics.max_opt().map(|v| v.to_string()),
+        Statistics::ByteArray(statistics) => statistics.max_opt().map(|v| match v.as_utf8() {
+            Ok(v) => v.to_string(),
+            Err(_) => v.to_string(),
+        }),
+        Statistics::FixedLenByteArray(statistics) => {
+            statistics.max_opt().map(|v| match v.as_utf8() {
+                Ok(v) => v.to_string(),
+                Err(_) => v.to_string(),
+            })
+        }
+    }
+}