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Add support for returning result rows as structs. (:as => :struct) #1011

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Add support for returning result rows as structs. (:as => :struct) #1011

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e05513c
add support for result rows as structs
errolgrannum Oct 22, 2018
74603cf
add rspec test for result rows as structs
errolgrannum Oct 22, 2018
bec7b61
add rspec test to ensure fields are always an array of symbols when a…
errolgrannum Oct 22, 2018
1793034
undo some unnecessary format changes to reduce diff noise
joe07734 Oct 30, 2018
92b7bed
factor out casting code
joe07734 Oct 30, 2018
cc237db
clean up spec
joe07734 Oct 30, 2018
c3b9847
a little more spec cleanup
joe07734 Oct 31, 2018
0204f00
use more compatible alternate name for rb_funcallv
joe07734 Nov 1, 2018
bfe0c3f
add unit test for statements
joe07734 Nov 1, 2018
db4a06d
rework how AS_HASH is assigned
joe07734 Nov 7, 2018
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92 changes: 69 additions & 23 deletions ext/mysql2/result.c
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Expand Up @@ -22,7 +22,7 @@ static rb_encoding *binaryEncoding;

typedef struct {
int symbolizeKeys;
int asArray;
int rowsAs;
int castBool;
int cacheRows;
int cast;
Expand All @@ -41,13 +41,21 @@ static VALUE sym_symbolize_keys, sym_as, sym_array, sym_database_timezone,
sym_application_timezone, sym_local, sym_utc, sym_cast_booleans,
sym_cache_rows, sym_cast, sym_stream, sym_name;

static VALUE sym_struct;

/* internal rowsAs constants */
#define AS_HASH 0
#define AS_ARRAY 1
#define AS_STRUCT 2

/* Mark any VALUEs that are only referenced in C, so the GC won't get them. */
static void rb_mysql_result_mark(void * wrapper) {
mysql2_result_wrapper * w = wrapper;
if (w) {
rb_gc_mark(w->fields);
rb_gc_mark(w->rows);
rb_gc_mark(w->encoding);
rb_gc_mark(w->rowStruct);
rb_gc_mark(w->client);
rb_gc_mark(w->statement);
}
Expand Down Expand Up @@ -287,6 +295,21 @@ static void rb_mysql_result_alloc_result_buffers(VALUE self, MYSQL_FIELD *fields
}
}

static VALUE cast_row_as_struct(VALUE self, VALUE rowVal, mysql2_result_wrapper *wrapper)
{
/* create struct from intermediate array */
if (wrapper->rowStruct == Qnil) {
unsigned int i;
VALUE *argv_fields = ALLOCA_N(VALUE, wrapper->numberOfFields);
for (i = 0; i < wrapper->numberOfFields; i++) {
argv_fields[i] = rb_mysql_result_fetch_field(self, i, 1);
}
wrapper->rowStruct = rb_funcall2(rb_cStruct, intern_new, (int) wrapper->numberOfFields, argv_fields);
}

return rb_struct_alloc(wrapper->rowStruct, rowVal);
}

static VALUE rb_mysql_result_fetch_row_stmt(VALUE self, MYSQL_FIELD * fields, const result_each_args *args)
{
VALUE rowVal;
Expand All @@ -303,11 +326,6 @@ static VALUE rb_mysql_result_fetch_row_stmt(VALUE self, MYSQL_FIELD * fields, co
wrapper->numberOfFields = mysql_num_fields(wrapper->result);
wrapper->fields = rb_ary_new2(wrapper->numberOfFields);
}
if (args->asArray) {
rowVal = rb_ary_new2(wrapper->numberOfFields);
} else {
rowVal = rb_hash_new();
}

if (wrapper->result_buffers == NULL) {
rb_mysql_result_alloc_result_buffers(self, fields);
Expand Down Expand Up @@ -336,6 +354,12 @@ static VALUE rb_mysql_result_fetch_row_stmt(VALUE self, MYSQL_FIELD * fields, co
}
}

if (args->rowsAs == AS_HASH) {
rowVal = rb_hash_new();
} else /* array or struct */ {
rowVal = rb_ary_new2(wrapper->numberOfFields);
}

for (i = 0; i < wrapper->numberOfFields; i++) {
VALUE field = rb_mysql_result_fetch_field(self, i, args->symbolizeKeys);
VALUE val = Qnil;
Expand Down Expand Up @@ -464,13 +488,17 @@ static VALUE rb_mysql_result_fetch_row_stmt(VALUE self, MYSQL_FIELD * fields, co
}
}

if (args->asArray) {
rb_ary_push(rowVal, val);
} else {
if (args->rowsAs == AS_HASH) {
rb_hash_aset(rowVal, field, val);
} else /* array or struct */ {
rb_ary_push(rowVal, val);
}
}

if (args->rowsAs == AS_STRUCT) {
rowVal = cast_row_as_struct(self, rowVal, wrapper);
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This is still using an intermediary array in the row fetch loop above. Is that better/more efficient to create the struct once than to incrementally add members to the struct in the same way elements are pushed into the array or added into the hash? I think the latter would have more clarity / all three options being handled as cases in the same loop.

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I was trying to avoid modifying the the main loop for clarity! It also allowed me to factor the "cast_row_as_struct" code with a simple parameter list. The statement support added a lot of duplicate code and I really wanted to not contribute to that. Also, the struct.new native call has a nice array form.

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Happy to rethink this if you think it's critical.

}

return rowVal;
}

Expand Down Expand Up @@ -498,10 +526,12 @@ static VALUE rb_mysql_result_fetch_row(VALUE self, MYSQL_FIELD * fields, const r
wrapper->numberOfFields = mysql_num_fields(wrapper->result);
wrapper->fields = rb_ary_new2(wrapper->numberOfFields);
}
if (args->asArray) {
rowVal = rb_ary_new2(wrapper->numberOfFields);
} else {

if (args->rowsAs == AS_HASH) {
rowVal = rb_hash_new();
} else /* array or struct */ {
/* struct uses array as an intermediary */
rowVal = rb_ary_new2(wrapper->numberOfFields);
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These don't get GC marked, why does the struct variant need to be GC marked? (w->rowStruct above) (Or conversely, should these also get GC marked?)

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I admit I'm hazy on when something needs to be gc-marked and when it doesn't. The "prototype" struct needs to be marked so that it'll stick around while control hops between the gem and ruby, while enumerating the results. Each row result struct, tho', is an instance of this prototype struct and is made right here, just like the hash and array, and returned to the client asap and will be gc marked there. That's my understanding anyway.

}
fieldLengths = mysql_fetch_lengths(wrapper->result);

Expand Down Expand Up @@ -671,19 +701,24 @@ static VALUE rb_mysql_result_fetch_row(VALUE self, MYSQL_FIELD * fields, const r
break;
}
}
if (args->asArray) {
rb_ary_push(rowVal, val);
} else {
if (args->rowsAs == AS_HASH) {
rb_hash_aset(rowVal, field, val);
} else /* array or struct */ {
rb_ary_push(rowVal, val);
}
} else {
if (args->asArray) {
rb_ary_push(rowVal, Qnil);
} else {
if (args->rowsAs == AS_HASH) {
rb_hash_aset(rowVal, field, Qnil);
} else /* array or struct */ {
rb_ary_push(rowVal, Qnil);
}
}
}

if (args->rowsAs == AS_STRUCT) {
rowVal = cast_row_as_struct(self, rowVal, wrapper);
}

return rowVal;
}

Expand All @@ -696,7 +731,7 @@ static VALUE rb_mysql_result_fetch_fields(VALUE self) {

defaults = rb_iv_get(self, "@query_options");
Check_Type(defaults, T_HASH);
if (rb_hash_aref(defaults, sym_symbolize_keys) == Qtrue) {
if (rb_hash_aref(defaults, sym_symbolize_keys) == Qtrue || rb_hash_aref(defaults, sym_as) == sym_struct) {
symbolizeKeys = 1;
}

Expand Down Expand Up @@ -807,9 +842,9 @@ static VALUE rb_mysql_result_each_(VALUE self,

static VALUE rb_mysql_result_each(int argc, VALUE * argv, VALUE self) {
result_each_args args;
VALUE defaults, opts, block, (*fetch_row_func)(VALUE, MYSQL_FIELD *fields, const result_each_args *args);
VALUE defaults, opts, as_opt, block, (*fetch_row_func)(VALUE, MYSQL_FIELD *fields, const result_each_args *args);
ID db_timezone, app_timezone, dbTz, appTz;
int symbolizeKeys, asArray, castBool, cacheRows, cast;
int symbolizeKeys, rowsAs, castBool, cacheRows, cast;

GET_RESULT(self);

Expand All @@ -826,11 +861,20 @@ static VALUE rb_mysql_result_each(int argc, VALUE * argv, VALUE self) {
}

symbolizeKeys = RTEST(rb_hash_aref(opts, sym_symbolize_keys));
asArray = rb_hash_aref(opts, sym_as) == sym_array;
castBool = RTEST(rb_hash_aref(opts, sym_cast_booleans));
cacheRows = RTEST(rb_hash_aref(opts, sym_cache_rows));
cast = RTEST(rb_hash_aref(opts, sym_cast));

as_opt = rb_hash_aref(opts, sym_as);
if (as_opt == sym_array) {
rowsAs = AS_ARRAY;
} else if (as_opt == sym_struct) {
rowsAs = AS_STRUCT;
symbolizeKeys = 1; /* force */
} else {
rowsAs = AS_HASH;
}

if (wrapper->is_streaming && cacheRows) {
rb_warn(":cache_rows is ignored if :stream is true");
}
Expand Down Expand Up @@ -879,7 +923,7 @@ static VALUE rb_mysql_result_each(int argc, VALUE * argv, VALUE self) {

// Backward compat
args.symbolizeKeys = symbolizeKeys;
args.asArray = asArray;
args.rowsAs = rowsAs;
args.castBool = castBool;
args.cacheRows = cacheRows;
args.cast = cast;
Expand Down Expand Up @@ -930,6 +974,7 @@ VALUE rb_mysql_result_to_obj(VALUE client, VALUE encoding, VALUE options, MYSQL_
wrapper->result = r;
wrapper->fields = Qnil;
wrapper->rows = Qnil;
wrapper->rowStruct = Qnil;
wrapper->encoding = encoding;
wrapper->streamingComplete = 0;
wrapper->client = client;
Expand Down Expand Up @@ -983,6 +1028,7 @@ void init_mysql2_result() {
sym_symbolize_keys = ID2SYM(rb_intern("symbolize_keys"));
sym_as = ID2SYM(rb_intern("as"));
sym_array = ID2SYM(rb_intern("array"));
sym_struct = ID2SYM(rb_intern("struct"));
sym_local = ID2SYM(rb_intern("local"));
sym_utc = ID2SYM(rb_intern("utc"));
sym_cast_booleans = ID2SYM(rb_intern("cast_booleans"));
Expand Down
1 change: 1 addition & 0 deletions ext/mysql2/result.h
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Expand Up @@ -10,6 +10,7 @@ typedef struct {
VALUE client;
VALUE encoding;
VALUE statement;
VALUE rowStruct;
my_ulonglong numberOfFields;
my_ulonglong numberOfRows;
unsigned long lastRowProcessed;
Expand Down
11 changes: 11 additions & 0 deletions spec/mysql2/result_spec.rb
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Expand Up @@ -72,6 +72,12 @@
end
end

it "should be able to return results as a struct" do
@result.each(as: :struct) do |row|
expect(row).to be_kind_of(Struct)
end
end

it "should cache previously yielded results by default" do
expect(@result.first.object_id).to eql(@result.first.object_id)
end
Expand Down Expand Up @@ -117,6 +123,11 @@
result = @client.query "SELECT 'a', 'b', 'c'"
expect(result.fields).to eql(%w[a b c])
end

it "should return field names as symbols if rows are structs" do
result = @client.query "SELECT 'a', 'b', 'c'", as: :struct
expect(result.fields.first).to be_an_instance_of(Symbol)
end
end

context "streaming" do
Expand Down
12 changes: 12 additions & 0 deletions spec/mysql2/statement_spec.rb
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Expand Up @@ -294,6 +294,13 @@ def stmt_count
end
end

it "should be able to return results as a struct" do
@result = @client.prepare("SELECT 1").execute(as: :struct)
@result.each do |row|
expect(row).to be_kind_of(Struct)
end
end

it "should cache previously yielded results by default" do
@result = @client.prepare("SELECT 1").execute
expect(@result.first.object_id).to eql(@result.first.object_id)
Expand Down Expand Up @@ -329,6 +336,11 @@ def stmt_count
expect(stmt.fields).to eql(%w[a b c])
end

it "should return field names as symbols if rows are structs" do
result = @client.prepare("SELECT 'a', 'b', 'c'").execute(as: :struct)
expect(result.fields.first).to be_an_instance_of(Symbol)
end

it "should return nil for statement with no result fields" do
stmt = @client.prepare("INSERT INTO mysql2_test () VALUES ()")
expect(stmt.fields).to eql(nil)
Expand Down