Implement ResultSourceMapping

pglablib/ResultSourceMapping.h

@@ -0,0 +1,61 @@
+#ifndef RESULTSOURCEMAPPING_H
+#define RESULTSOURCEMAPPING_H
+
+#include <libpq-fe.h>
+
+#include <vector>
+
+class PgDatabaseCatalog;
+
+namespace Pgsql {
+    class Result;
+}
+
+/// The table column a result column is read from, as reported by libpq (PQftable/PQftablecol).
+/// tableOid is InvalidOid and attnum is 0 for expression columns.
+struct ResultColumnSource {
+    Oid tableOid = InvalidOid;
+    int attnum = 0;
+};
+
+/// The primary key of a table, attnums in key order.
+struct TablePrimaryKey {
+    Oid tableOid = InvalidOid;
+    std::vector<int> attnums;
+};
+
+/// Maps the columns of a query result to the table columns they come from and decides which
+/// cells can be edited. A cell is editable when it maps to a user column of a table whose full
+/// primary key is present in the result and which is not ambiguous.
+class ResultSourceMapping {
+public:
+    ResultSourceMapping(std::vector<ResultColumnSource> columns, const std::vector<TablePrimaryKey> &primaryKeys);
+
+    int columnCount() const;
+    /// Table the column is read from, InvalidOid for expression columns.
+    Oid tableOid(int col) const;
+    /// attnum of the column in its table, 0 for expression columns.
+    int attnum(int col) const;
+    bool isEditable(int col) const;
+    /// Result column indices holding the primary key of the table, in key order.
+    /// Empty when the table is not editable.
+    std::vector<int> primaryKeyColumns(Oid tableOid) const;
+
+private:
+    struct TableInfo {
+        Oid tableOid = InvalidOid;
+        bool editable = false;
+        std::vector<int> pkColumns;
+    };
+
+    std::vector<ResultColumnSource> m_columns;
+    std::vector<TableInfo> m_tables;
+
+    const TableInfo *findTable(Oid tableOid) const;
+};
+
+/// Builds the mapping for a query result, looking up the primary keys of the source tables in the catalog.
+ResultSourceMapping createResultSourceMapping(const Pgsql::Result &result, const PgDatabaseCatalog &catalog);
+
+
+#endif // RESULTSOURCEMAPPING_H