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Session(database, labels=None)Representation of a Cloud Spanner Session.
We can use a Session to:
createthe session- Use
existsto check for the existence of the session dropthe session
Parameters | |
|---|---|
| Name | Description |
database |
Database
The database to which the session is bound. |
labels |
dict (str -> str)
(Optional) User-assigned labels for the session. |
Properties
labels
User-assigned labels for the session.
| Returns | |
|---|---|
| Type | Description |
dict (str -> str) | the labels dict (empty if no labels were assigned. |
name
Session name used in requests.
"projects/../instances/../databases/../sessions/{session_id}"
| Exceptions | |
|---|---|
| Type | Description |
ValueError | if session is not yet created |
| Returns | |
|---|---|
| Type | Description |
str | The session name. |
session_id
Read-only ID, set by the back-end during create.
Methods
batch
batch()Factory to create a batch for this session.
| Exceptions | |
|---|---|
| Type | Description |
ValueError | if the session has not yet been created. |
| Returns | |
|---|---|
| Type | Description |
Batch | a batch bound to this session |
create
create()Create this session, bound to its database.
| Exceptions | |
|---|---|
| Type | Description |
`ValueError | if session_id is already set. |
delete
delete()Delete this session.
| Exceptions | |
|---|---|
| Type | Description |
ValueError | if session_id is not already set. |
NotFound | if the session does not exist |
execute_sql
execute_sql(sql, params=None, param_types=None, query_mode=None, query_options=None, retry=<_MethodDefault._DEFAULT_VALUE: <object object>>, timeout=<_MethodDefault._DEFAULT_VALUE: <object object>>)Perform an ExecuteStreamingSql API request.
| Parameters | |
|---|---|
| Name | Description |
sql |
str
SQL query statement |
params |
dict, {str -> column value}
values for parameter replacement. Keys must match the names used in |
param_types |
dict, {str ->
(Optional) explicit types for one or more param values; overrides default type detection on the back-end. |
query_mode |
Mode governing return of results / query plan. See: |
query_options |
QueryOptions or
(Optional) Options that are provided for query plan stability. |
| Returns | |
|---|---|
| Type | Description |
StreamedResultSet | a result set instance which can be used to consume rows. |
exists
exists()Test for the existence of this session.
| Returns | |
|---|---|
| Type | Description |
bool | True if the session exists on the back-end, else False. |
ping
ping()Ping the session to keep it alive by executing "SELECT 1".
| Exceptions | |
|---|---|
| Type | Description |
ValueError | if session_id is not already set. |
read
read(table, columns, keyset, index="", limit=0)Perform a StreamingRead API request for rows in a table.
| Parameters | |
|---|---|
| Name | Description |
table |
str
name of the table from which to fetch data |
columns |
list of str
names of columns to be retrieved |
keyset |
KeySet
keys / ranges identifying rows to be retrieved |
index |
str
(Optional) name of index to use, rather than the table's primary key |
limit |
int
(Optional) maximum number of rows to return |
| Returns | |
|---|---|
| Type | Description |
StreamedResultSet | a result set instance which can be used to consume rows. |
run_in_transaction
run_in_transaction(func, *args, **kw)Perform a unit of work in a transaction, retrying on abort.
| Parameters | |
|---|---|
| Name | Description |
args |
tuple
additional positional arguments to be passed to |
kw |
dict
(Optional) keyword arguments to be passed to |
func |
callable
takes a required positional argument, the transaction, and additional positional / keyword arguments as supplied by the caller. |
| Exceptions | |
|---|---|
| Type | Description |
Exception | reraises any non-ABORT execptions raised by func. |
| Returns | |
|---|---|
| Type | Description |
Any | The return value of func. |
snapshot
snapshot(**kw)Create a snapshot to perform a set of reads with shared staleness.
| Parameter | |
|---|---|
| Name | Description |
kw |
dict
Passed through to Snapshot ctor. |
| Exceptions | |
|---|---|
| Type | Description |
ValueError | if the session has not yet been created. |
| Returns | |
|---|---|
| Type | Description |
Snapshot | a snapshot bound to this session |
transaction
transaction()Create a transaction to perform a set of reads with shared staleness.
| Exceptions | |
|---|---|
| Type | Description |
ValueError | if the session has not yet been created. |
| Returns | |
|---|---|
| Type | Description |
Transaction | a transaction bound to this session |