Hello! I recommend starting with H2TreeIndex class. Maybe dropping mails on developer list with precise questions.
Regards, -- Ilya Kasnacheev пн, 17 сент. 2018 г. в 16:25, eugene miretsky <eugene.miret...@gmail.com>: > Thanks! > > I am curious about the process of loading data from Ignite to H2 on the > fly, as H2 creating indexes but storing them in Ignite. Can you point me to > some JIRAs that discuss it, or which part of the code is responsible for > that? > > On Mon, Sep 17, 2018 at 9:18 AM Ilya Kasnacheev <ilya.kasnach...@gmail.com> > wrote: > >> Hello! >> >> 1. 1. H2 executes the query, during which it has to load rows from >> tables, and Ignite does the row loading part. Then Ignite will collect >> query results on all nodes and aggregate them on a single node. >> 1. 2. Index is created by H2, but it is stored in Ignite pages (?). >> 2. Maybe you're right, I have to admit I'm unfamiliar with precise >> details here. >> >> Regards, >> -- >> Ilya Kasnacheev >> >> >> пн, 17 сент. 2018 г. в 16:02, eugene miretsky <eugene.miret...@gmail.com >> >: >> >>> Thanks! >>> >>> >>> 1. >>> 1. "Ignite feeds H2 rows that it asks for, and H2 creates indexes >>> on them and executes queries on them." - what exactly do you mean by >>> that? >>> Do you mean that all parts of a query that use indexes are executed >>> by H2, >>> then the actual data is retrieved from Ignite pages, and the final >>> (non-indexed) parts of the query executed by Ignite? >>> 2. What happens when I create an index on a new column? Is the >>> index created in Ignite (and stored in Ignite pages?), or is it >>> created in >>> H2? >>> 2. The reason I was asking about AFFINITY_KEY, _key_PK and >>> _key_PK_hash indexed is that in this code >>> >>> <https://github.com/apache/ignite/blob/56975c266e7019f307bb9da42333a6db4e47365e/modules/indexing/src/main/java/org/apache/ignite/internal/processors/query/h2/H2TableDescriptor.java> >>> it >>> looks like they are created in H2 >>> >>> >>> >>> On Mon, Sep 17, 2018 at 8:36 AM Ilya Kasnacheev < >>> ilya.kasnach...@gmail.com> wrote: >>> >>>> Hello! >>>> >>>> 1. H2 does not store data but, as far as my understanding goes, it >>>> created SQL indexes from data. Ignite feeds H2 rows that it asks for, and >>>> H2 creates indexes on them and executes queries on them. >>>> 2. Ignite always has special index on your key (since it's a key-value >>>> storage it can always find tuple by key). Ignite is also aware of key's >>>> hash code, and affinity key value always maps to one partition of data (of >>>> 1024 by default). Those are not H2 indexes and they're mostly used on >>>> planning stage. E.g. you can map query to one node if affinity key is >>>> present in the request. >>>> 3. Data is brought onto the heap to read any fields from row. GROUP BY >>>> will hold its tuples on heap. Ignite has configurable index inlining where >>>> you can avoid reading objects from heap just to access indexed fields. >>>> 4. With GROUP BY, lazy evaluation will not help you much. It will still >>>> have to hold all data on heap at some point. Lazy evaluation mostly helps >>>> with "SELECT * FROM table" type queries which provide very large and boring >>>> result set. >>>> >>>> Hope this helps. >>>> -- >>>> Ilya Kasnacheev >>>> >>>> >>>> пт, 14 сент. 2018 г. в 17:39, eugene miretsky < >>>> eugene.miret...@gmail.com>: >>>> >>>>> Hello, >>>>> >>>>> Trying to understand how exactly SQL queries are executed in Ignite. A >>>>> few questions >>>>> >>>>> >>>>> 1. To what extent is H2 used? Does it store the data? Does it >>>>> create the indexes? Is it used only for generating execution plans? I >>>>> believe that all the data used to be stored in H2, but with the new >>>>> durable >>>>> memory architecture, I believe that's no longer the case. >>>>> 2. Which indexes are used? Ignite creates B+ tree indexes and >>>>> stores them in Index pages, but I also see AFFINITY_KEY, _key_PK and >>>>> _key_PK_hash indexes created in H2. >>>>> 3. When is data brought onto the heap? I am assuming that groupby >>>>> and aggregate require all the matching queries to first be copied from >>>>> off-heap to heap >>>>> 4. How does lazy evaluation work? For example, for group_by, does >>>>> it bring batches of matching records with the same group_by key onto >>>>> the >>>>> heap? >>>>> >>>>> I am not necessarily looking for the exact answers, but rather pointer >>>>> in the right direction (documentation, code, jiras) >>>>> >>>>> Cheers, >>>>> Eugene >>>>> >>>>
