docs: document inlining of small data in read_* APIs (#670)

* docs: document inlining of small data in `read_*` APIs * mention that threshold is in memory size * non-bigquery instead of non-"bigquery"

Author: shobsi

bigframes/session/__init__.py

@@ -874,6 +874,11 @@ def read_pandas(
  The pandas DataFrame will be persisted as a temporary BigQuery table, which can be
  automatically recycled after the Session is closed.
 
+ .. note::
+ Data is inlined in the query SQL if it is small enough (roughly 5MB
+ or less in memory). Larger size data is loaded to a BigQuery table
+ instead.
+
  **Examples:**
 
  >>> import bigframes.pandas as bpd

third_party/bigframes_vendored/pandas/io/parquet.py

@@ -19,6 +19,11 @@ def read_parquet(
  Instead, set a serialized index column as the index and sort by
  that in the resulting DataFrame.
 
+ .. note::
+ For non-"bigquery" engine, data is inlined in the query SQL if it is
+ small enough (roughly 5MB or less in memory). Larger size data is
+ loaded to a BigQuery table instead.
+
  **Examples:**
 
  >>> import bigframes.pandas as bpd

third_party/bigframes_vendored/pandas/io/parsers/readers.py

@@ -62,6 +62,11 @@ def read_csv(
  file. Instead, set a serialized index column as the index and sort by
  that in the resulting DataFrame.
 
+ .. note::
+ For non-bigquery engine, data is inlined in the query SQL if it is
+ small enough (roughly 5MB or less in memory). Larger size data is
+ loaded to a BigQuery table instead.
+
  **Examples:**
 
  >>> import bigframes.pandas as bpd
@@ -167,6 +172,11 @@ def read_json(
  file. Instead, set a serialized index column as the index and sort by
  that in the resulting DataFrame.
 
+ .. note::
+ For non-bigquery engine, data is inlined in the query SQL if it is
+ small enough (roughly 5MB or less in memory). Larger size data is
+ loaded to a BigQuery table instead.
+
  **Examples:**
 
  >>> import bigframes.pandas as bpd

third_party/bigframes_vendored/pandas/io/pickle.py

@@ -25,6 +25,11 @@ def read_pickle(
  If the content of the pickle file is a Series and its name attribute is None,
  the name will be set to '0' by default.
 
+ .. note::
+ Data is inlined in the query SQL if it is small enough (roughly 5MB
+ or less in memory). Larger size data is loaded to a BigQuery table
+ instead.
+
  **Examples:**
 
  >>> import bigframes.pandas as bpd