diff options
Diffstat (limited to 'doc/src/sgml/ref')
| -rw-r--r-- | doc/src/sgml/ref/create_aggregate.sgml | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/doc/src/sgml/ref/create_aggregate.sgml b/doc/src/sgml/ref/create_aggregate.sgml index 222e0aa5c9d..0472ac2e874 100644 --- a/doc/src/sgml/ref/create_aggregate.sgml +++ b/doc/src/sgml/ref/create_aggregate.sgml @@ -384,9 +384,13 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1; <para> The approximate average size (in bytes) of the aggregate's state value. If this parameter is omitted or is zero, a default estimate is used - based on the <replaceable>state_data_type</replaceable>. + based on the <replaceable>state_data_type</replaceable>. If set to a + negative value, it indicates the state data can grow unboundedly in + size, such as when the aggregate accumulates input rows (e.g., + array_agg, string_agg). The planner uses this value to estimate the memory required for a - grouped aggregate query. + grouped aggregate query and to avoid optimizations that may cause + excessive memory usage. </para> </listitem> </varlistentry> @@ -568,7 +572,8 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1; <para> The approximate average size (in bytes) of the aggregate's state value, when using moving-aggregate mode. This works the same as - <replaceable>state_data_size</replaceable>. + <replaceable>state_data_size</replaceable>, except that negative + values are not used to indicate unbounded state size. </para> </listitem> </varlistentry> |