[SPARK-3299][SQL]Public API in SQLContext to list tables

https://issues.apache.org/jira/browse/SPARK-3299

Author: Yin Huai <yhuai@databricks.com>

Closes #4547 from yhuai/tables and squashes the following commits:

6c8f92e [Yin Huai] Add tableNames.
acbb281 [Yin Huai] Update Python test.
7793dcb [Yin Huai] Fix scala test.
572870d [Yin Huai] Address comments.
aba2e88 [Yin Huai] Format.
12c86df [Yin Huai] Add tables() to SQLContext to return a DataFrame containing existing tables.

1 files changed, 34 insertions, 0 deletions

diff --git a/python/pyspark/sql/context.py b/python/pyspark/sql/context.py
index db4bcbece2..082f1b691b 100644
--- a/python/pyspark/sql/context.py
+++ b/python/pyspark/sql/context.py
@@ -621,6 +621,40 @@ class SQLContext(object):
         """
         return DataFrame(self._ssql_ctx.table(tableName), self)
 
+    def tables(self, dbName=None):
+        """Returns a DataFrame containing names of tables in the given database.
+
+        If `dbName` is not specified, the current database will be used.
+
+        The returned DataFrame has two columns, tableName and isTemporary
+        (a column with BooleanType indicating if a table is a temporary one or not).
+
+        >>> sqlCtx.registerRDDAsTable(df, "table1")
+        >>> df2 = sqlCtx.tables()
+        >>> df2.filter("tableName = 'table1'").first()
+        Row(tableName=u'table1', isTemporary=True)
+        """
+        if dbName is None:
+            return DataFrame(self._ssql_ctx.tables(), self)
+        else:
+            return DataFrame(self._ssql_ctx.tables(dbName), self)
+
+    def tableNames(self, dbName=None):
+        """Returns a list of names of tables in the database `dbName`.
+
+        If `dbName` is not specified, the current database will be used.
+
+        >>> sqlCtx.registerRDDAsTable(df, "table1")
+        >>> "table1" in sqlCtx.tableNames()
+        True
+        >>> "table1" in sqlCtx.tableNames("db")
+        True
+        """
+        if dbName is None:
+            return [name for name in self._ssql_ctx.tableNames()]
+        else:
+            return [name for name in self._ssql_ctx.tableNames(dbName)]
+
     def cacheTable(self, tableName):
         """Caches the specified table in-memory."""
         self._ssql_ctx.cacheTable(tableName)