| 1 |
|
%% RSM logic lives here |
| 2 |
|
-module(mam_lookup). |
| 3 |
|
-export([lookup/3]). |
| 4 |
|
|
| 5 |
|
-include("mongoose.hrl"). |
| 6 |
|
-include("jlib.hrl"). |
| 7 |
|
-include("mongoose_rsm.hrl"). |
| 8 |
|
|
| 9 |
|
-type filter() :: mam_filter:filter(). |
| 10 |
|
-type env_vars() :: mod_mam_rdbms_arch:env_vars(). |
| 11 |
|
-type params() :: map(). |
| 12 |
|
-type message_id() :: mod_mam:message_id(). |
| 13 |
|
-type maybe_rsm() :: #rsm_in{} | undefined. |
| 14 |
|
-type opt_count_type() :: last_page | by_offset | none. |
| 15 |
|
|
| 16 |
|
%% Public logic |
| 17 |
|
%% We use two fields from Env: |
| 18 |
|
%% - lookup_fn |
| 19 |
|
%% - decode_row_fn |
| 20 |
|
-spec lookup(env_vars(), filter(), params()) -> |
| 21 |
|
{ok, mod_mam:lookup_result()} | {error, item_not_found}. |
| 22 |
|
lookup(Env = #{}, Filter, Params = #{rsm := RSM}) when is_list(Filter) -> |
| 23 |
:-( |
OptParams = Params#{opt_count_type => opt_count_type(RSM)}, |
| 24 |
:-( |
choose_lookup_messages_strategy(Env, Filter, OptParams). |
| 25 |
|
|
| 26 |
|
lookup_query(QueryType, #{lookup_fn := LookupF} = Env, Filters, Order, OffsetLimit) -> |
| 27 |
:-( |
LookupF(QueryType, Env, Filters, Order, OffsetLimit). |
| 28 |
|
|
| 29 |
|
decode_row(Row, #{decode_row_fn := DecodeF} = Env) -> |
| 30 |
:-( |
DecodeF(Row, Env). |
| 31 |
|
|
| 32 |
|
%% Private logic below |
| 33 |
|
|
| 34 |
|
%% There are no optimizations for these queries yet: |
| 35 |
|
%% - #rsm_in{direction = aft, id = ID} |
| 36 |
|
%% - #rsm_in{direction = before, id = ID} |
| 37 |
|
-spec opt_count_type(RSM :: maybe_rsm()) -> opt_count_type(). |
| 38 |
|
opt_count_type(#rsm_in{direction = before, id = undefined}) -> |
| 39 |
:-( |
last_page; %% last page is supported |
| 40 |
|
opt_count_type(#rsm_in{direction = undefined}) -> |
| 41 |
:-( |
by_offset; %% offset |
| 42 |
|
opt_count_type(undefined) -> |
| 43 |
:-( |
by_offset; %% no RSM |
| 44 |
|
opt_count_type(_) -> |
| 45 |
:-( |
none. %% id field is defined in RSM |
| 46 |
|
|
| 47 |
|
%% There are several strategies how to extract messages: |
| 48 |
|
%% - we can use regular query that requires counting; |
| 49 |
|
%% - we can reduce number of queries if we skip counting for small data sets; |
| 50 |
|
%% - sometimes we want not to count at all |
| 51 |
|
%% (for example, our client side counts ones and keep the information) |
| 52 |
|
choose_lookup_messages_strategy(Env, Filter, |
| 53 |
|
Params = #{rsm := RSM, page_size := PageSize}) -> |
| 54 |
:-( |
case Params of |
| 55 |
|
#{is_simple := true} -> |
| 56 |
|
%% Simple query without calculating offset and total count |
| 57 |
:-( |
simple_lookup_messages(Env, RSM, PageSize, Filter); |
| 58 |
|
#{opt_count_type := last_page} when PageSize > 0 -> |
| 59 |
|
%% Extract messages before calculating offset and total count |
| 60 |
|
%% Useful for small result sets |
| 61 |
:-( |
lookup_last_page(Env, PageSize, Filter); |
| 62 |
|
#{opt_count_type := by_offset} when PageSize > 0 -> |
| 63 |
|
%% Extract messages before calculating offset and total count |
| 64 |
|
%% Useful for small result sets |
| 65 |
:-( |
lookup_by_offset(Env, RSM, PageSize, Filter); |
| 66 |
|
_ -> |
| 67 |
|
%% Calculate offset and total count first before extracting messages |
| 68 |
:-( |
lookup_messages_regular(Env, RSM, PageSize, Filter) |
| 69 |
|
end. |
| 70 |
|
|
| 71 |
|
%% Just extract messages without count and offset information |
| 72 |
|
simple_lookup_messages(Env, RSM, PageSize, Filter) -> |
| 73 |
:-( |
{Filter2, Offset, Order} = rsm_to_filter(RSM, Filter), |
| 74 |
:-( |
Messages = extract_messages(Env, Filter2, Offset, PageSize, Order), |
| 75 |
:-( |
{ok, {undefined, undefined, Messages}}. |
| 76 |
|
|
| 77 |
|
rsm_to_filter(RSM, Filter) -> |
| 78 |
:-( |
case RSM of |
| 79 |
|
%% Get last rows from result set |
| 80 |
|
#rsm_in{direction = aft, id = ID} -> |
| 81 |
:-( |
{after_id(ID, Filter), 0, asc}; |
| 82 |
|
#rsm_in{direction = before, id = undefined} -> |
| 83 |
:-( |
{Filter, 0, desc}; |
| 84 |
|
#rsm_in{direction = before, id = ID} -> |
| 85 |
:-( |
{before_id(ID, Filter), 0, desc}; |
| 86 |
|
#rsm_in{direction = undefined, index = Index} -> |
| 87 |
:-( |
{Filter, Index, asc}; |
| 88 |
|
undefined -> |
| 89 |
:-( |
{Filter, 0, asc} |
| 90 |
|
end. |
| 91 |
|
|
| 92 |
|
%% This function handles case: #rsm_in{direction = before, id = undefined} |
| 93 |
|
%% Assumes assert_rsm_without_id(RSM) |
| 94 |
|
lookup_last_page(Env, PageSize, Filter) -> |
| 95 |
:-( |
Messages = extract_messages(Env, Filter, 0, PageSize, desc), |
| 96 |
:-( |
Selected = length(Messages), |
| 97 |
:-( |
Offset = |
| 98 |
|
case Selected < PageSize of |
| 99 |
|
true -> |
| 100 |
:-( |
0; %% Result fits on a single page |
| 101 |
|
false -> |
| 102 |
:-( |
FirstID = decoded_row_to_message_id(hd(Messages)), |
| 103 |
:-( |
calc_count(Env, before_id(FirstID, Filter)) |
| 104 |
|
end, |
| 105 |
:-( |
{ok, {Offset + Selected, Offset, Messages}}. |
| 106 |
|
|
| 107 |
|
lookup_by_offset(Env, RSM, PageSize, Filter) -> |
| 108 |
:-( |
assert_rsm_without_id(RSM), |
| 109 |
:-( |
Offset = rsm_to_index(RSM), |
| 110 |
:-( |
Messages = extract_messages(Env, Filter, Offset, PageSize, asc), |
| 111 |
:-( |
Selected = length(Messages), |
| 112 |
:-( |
TotalCount = |
| 113 |
|
case Selected < PageSize of |
| 114 |
|
true -> |
| 115 |
:-( |
Offset + Selected; %% Result fits on a single page |
| 116 |
|
false -> |
| 117 |
:-( |
LastID = decoded_row_to_message_id(lists:last(Messages)), |
| 118 |
:-( |
CountAfterLastID = calc_count(Env, after_id(LastID, Filter)), |
| 119 |
:-( |
Offset + Selected + CountAfterLastID |
| 120 |
|
end, |
| 121 |
:-( |
{ok, {TotalCount, Offset, Messages}}. |
| 122 |
|
|
| 123 |
:-( |
assert_rsm_without_id(undefined) -> ok; |
| 124 |
:-( |
assert_rsm_without_id(#rsm_in{id = undefined}) -> ok. |
| 125 |
|
|
| 126 |
|
rsm_to_index(#rsm_in{direction = undefined, index = Offset}) |
| 127 |
:-( |
when is_integer(Offset) -> Offset; |
| 128 |
:-( |
rsm_to_index(_) -> 0. |
| 129 |
|
|
| 130 |
|
lookup_messages_regular(Env, RSM, PageSize, Filter) -> |
| 131 |
:-( |
TotalCount = calc_count(Env, Filter), |
| 132 |
:-( |
Offset = calc_offset(Env, Filter, PageSize, TotalCount, RSM), |
| 133 |
:-( |
{LookupById, Filter2, Offset2, PageSize2, Order} = |
| 134 |
|
rsm_to_regular_lookup_vars(RSM, Filter, Offset, PageSize), |
| 135 |
:-( |
Messages = extract_messages(Env, Filter2, Offset2, PageSize2, Order), |
| 136 |
:-( |
Result = {TotalCount, Offset, Messages}, |
| 137 |
:-( |
case LookupById of |
| 138 |
|
true -> %% check if we've selected a message with #rsm_in.id |
| 139 |
:-( |
mod_mam_utils:check_for_item_not_found(RSM, PageSize, Result); |
| 140 |
|
false -> |
| 141 |
:-( |
{ok, Result} |
| 142 |
|
end. |
| 143 |
|
|
| 144 |
|
rsm_to_regular_lookup_vars(RSM, Filter, Offset, PageSize) -> |
| 145 |
:-( |
case RSM of |
| 146 |
|
#rsm_in{direction = aft, id = ID} when ID =/= undefined -> |
| 147 |
|
%% Set extra flag when selecting PageSize + 1 messages |
| 148 |
:-( |
{true, from_id(ID, Filter), 0, PageSize + 1, asc}; |
| 149 |
|
#rsm_in{direction = before, id = ID} when ID =/= undefined -> |
| 150 |
:-( |
{true, to_id(ID, Filter), 0, PageSize + 1, desc}; |
| 151 |
|
_ -> |
| 152 |
:-( |
{false, Filter, Offset, PageSize, asc} |
| 153 |
|
end. |
| 154 |
|
|
| 155 |
|
decode_rows(MessageRows, Env) -> |
| 156 |
:-( |
[decode_row(Row, Env) || Row <- MessageRows]. |
| 157 |
|
|
| 158 |
|
-spec decoded_row_to_message_id(mod_mam:message_row()) -> mod_mam:message_id(). |
| 159 |
:-( |
decoded_row_to_message_id(#{id := MessId}) -> MessId. |
| 160 |
|
|
| 161 |
|
-spec extract_messages(Env :: env_vars(), |
| 162 |
|
Filter :: filter(), Offset :: non_neg_integer(), Max :: pos_integer(), |
| 163 |
|
Order :: asc | desc) -> [mod_mam:message_row()]. |
| 164 |
|
extract_messages(_Env, _Filter, _Offset, 0 = _Max, _Order) -> |
| 165 |
:-( |
[]; |
| 166 |
|
extract_messages(Env, Filter, Offset, Max, Order) -> |
| 167 |
:-( |
{selected, MessageRows} = extract_rows(Env, Filter, Offset, Max, Order), |
| 168 |
:-( |
Rows = maybe_reverse(Order, MessageRows), |
| 169 |
:-( |
decode_rows(Rows, Env). |
| 170 |
|
|
| 171 |
:-( |
maybe_reverse(asc, List) -> List; |
| 172 |
:-( |
maybe_reverse(desc, List) -> lists:reverse(List). |
| 173 |
|
|
| 174 |
|
extract_rows(Env, Filters, Offset, Max, Order) -> |
| 175 |
:-( |
lookup_query(lookup, Env, Filters, Order, {Offset, Max}). |
| 176 |
|
|
| 177 |
|
%% @doc Get the total result set size. |
| 178 |
|
%% SELECT COUNT(*) as count FROM mam_message |
| 179 |
|
-spec calc_count(env_vars(), filter()) -> non_neg_integer(). |
| 180 |
|
calc_count(Env, Filter) -> |
| 181 |
:-( |
Result = lookup_query(count, Env, Filter, unordered, all), |
| 182 |
:-( |
mongoose_rdbms:selected_to_integer(Result). |
| 183 |
|
|
| 184 |
|
%% @doc Calculate a zero-based index of the row with UID in the result test. |
| 185 |
|
%% |
| 186 |
|
%% If the element does not exists, the ID of the next element will |
| 187 |
|
%% be returned instead. |
| 188 |
|
%% @end |
| 189 |
|
%% SELECT COUNT(*) as index FROM mam_message WHERE id <= ? |
| 190 |
|
-spec calc_index(env_vars(), filter(), message_id()) -> non_neg_integer(). |
| 191 |
|
calc_index(Env, Filter, ID) -> |
| 192 |
:-( |
calc_count(Env, to_id(ID, Filter)). |
| 193 |
|
|
| 194 |
|
%% @doc Count of elements in RSet before the passed element. |
| 195 |
|
%% |
| 196 |
|
%% The element with the passed UID can be already deleted. |
| 197 |
|
%% @end |
| 198 |
|
%% SELECT COUNT(*) as count FROM mam_message WHERE id < ? |
| 199 |
|
-spec calc_before(env_vars(), filter(), message_id()) -> non_neg_integer(). |
| 200 |
|
calc_before(Env, Filter, ID) -> |
| 201 |
:-( |
calc_count(Env, before_id(ID, Filter)). |
| 202 |
|
|
| 203 |
|
-spec calc_offset(Env :: env_vars(), |
| 204 |
|
Filter :: filter(), PageSize :: non_neg_integer(), |
| 205 |
|
TotalCount :: non_neg_integer(), RSM :: jlib:rsm_in()) -> non_neg_integer(). |
| 206 |
|
calc_offset(Env, Filter, PageSize, TotalCount, RSM) -> |
| 207 |
:-( |
case RSM of |
| 208 |
|
#rsm_in{direction = undefined, index = Index} when is_integer(Index) -> |
| 209 |
:-( |
Index; |
| 210 |
|
#rsm_in{direction = before, id = undefined} -> |
| 211 |
|
%% Requesting the Last Page in a Result Set |
| 212 |
:-( |
max(0, TotalCount - PageSize); |
| 213 |
|
#rsm_in{direction = before, id = ID} when is_integer(ID) -> |
| 214 |
:-( |
max(0, calc_before(Env, Filter, ID) - PageSize); |
| 215 |
|
#rsm_in{direction = aft, id = ID} when is_integer(ID) -> |
| 216 |
:-( |
calc_index(Env, Filter, ID); |
| 217 |
|
_ -> |
| 218 |
:-( |
0 |
| 219 |
|
end. |
| 220 |
|
|
| 221 |
|
-spec after_id(message_id(), filter()) -> filter(). |
| 222 |
|
after_id(ID, Filter) -> |
| 223 |
:-( |
[{greater, id, ID}|Filter]. |
| 224 |
|
|
| 225 |
|
-spec before_id(message_id(), filter()) -> filter(). |
| 226 |
|
before_id(ID, Filter) -> |
| 227 |
:-( |
[{less, id, ID}|Filter]. |
| 228 |
|
|
| 229 |
|
-spec from_id(message_id(), filter()) -> filter(). |
| 230 |
|
from_id(ID, Filter) -> |
| 231 |
:-( |
[{ge, id, ID}|Filter]. |
| 232 |
|
|
| 233 |
|
-spec to_id(message_id(), filter()) -> filter(). |
| 234 |
|
to_id(ID, Filter) -> |
| 235 |
:-( |
[{le, id, ID}|Filter]. |